How to properly call parentheses list elements in Prolog

Regards, i have the next knowledge base:

linea(1,[observatorio,tacubaya,juanacatlan,chapultepec,sevilla,cuahtemoc,
	 balderas,salto_del_agua,isabel_la_catolica,pino_suarez,merced,
	 candelaria,san_lazaro,moctezuma,balbuena,bulevard_puerto_aereo,
	 gomez_farias,zaragoza,pantitlan]
linea(2,[cuatro_caminos,panteones,tacuba,cuitlahuac,popotla,colegio_militar,
	 normal,san_cosme,revolucion,hidalgo,bellas_artes,allende,zocalo,
	 pino_suarez,san_antonio_abad,chabacano,viaducto,xola,villa_de_cortes,
	 nativitas,portales,ermita,general_anaya,tasquena]).
linea(3,[indios_verdes,deportivo_18_de_marzo,potrero,la_raza,tlatelolco,
	 guerrero,hidalgo,juarez,balderas,nignos_heroes,hospital_general,
	 centro_medico,etiopia,eugenia,division_del_norte,zapata,coyoacan,
	 viveros,miguel_angel_de_quevedo,copilco,universidad]).
linea(4,[martin_carrera,talisman,bondojito,consulado,canal_del_norte,
	 morelos,candelaria,fray_servando,jamaica,santa_anita]).
linea(5,[politecnico,instituto_del_petroleo,autobuses_norte,la_raza,misterios,
	 valle_gomez,consulado,eduardo_molina,aragon,oceania,terminal_aerea,
	 hangares,pantitlan]).
linea(6,[el_rosario,tezozomoc,azcapotzalco,ferreria,norte_45,vallejo,
	 instituto_del_petroleo,lindavista,deportivo_18_de_marzo,basilica,
	 martin_carrera]).
linea(7,[el_rosario,aquiles_serdan,camarones,refineria,tacuba,
	 rio_san_joaquin,polanco,auditorio,constituyentes,tacubaya,
	 san_pedro_de_los_pinos,san_antonio,mixcoac,barranca_del_muerto]).
linea(8,[garibaldi,bellas_artes,san_juan_de_letran,salto_del_agua,
	 doctores,obrera,chabacano,la_viga,santa_anita,coyuya,iztacalco,
	 apatlaco,aculco,escuadron_201,atlalilco,iztapalapa,
	 cerro_de_la_estrella,uami,constitucion_de_1917]).
linea(9,[tacubaya,patriotismo,chilpancingo,centro_medico,lazaro_cardenas,
	 chabacano,jamaica,mixihuca,velodromo,ciudad_deportiva,puebla,
	 pantitlan]).
linea(a,[pantitlan, agricola_oriental,canal_de_san_juan,tepalcates,guelatao,
	 pegnon_viejo,acatitla,santa_marta,los_reyes,la_paz]).
linea(b,[ciudad_azteca,plaza_aragon,olimpica,ecatepec,muzquiz,
	 rio_de_los_remedios,impulsora,nezahualcoyotl,villa_de_aragon,
	 bosque_de_aragon,deportivo_oceania,oceania,romero_rubio,
	 r_flores_magon,san_lazaro,morelos,tepito,lagunilla,garibaldi,
	 guerrero,buenavista]).
linea(12,[mixcoac,insurgentes_sur,hospital_20_de_noviembre,zapata,
	  parque_de_los_venados,eje_central,ermita,mexicaltzingo,
	  atlalico,culhuacan,san_andres_tomatlan,lomas_estrella,calle_11,
	  periferico_oriente,tezonco,olivos,nopalera,zapotitlan,
	  tlaltenco,tlahuac]).

... and the next functions:

member(X,[X|Xs]).
member(X,[Y|Xs]):-member(X,Xs).

append([],X,X).
append([X|Xs],Ys,[X|Zs]):-append(Xs,Ys,Zs).

What i'm trying to do is to check, for example, if the element 'mixcoac' belongs to the linea(12)'s array which is something like the 2nd element, but i don't know how to work this kind of lists in the Prolog syntax.

I tried to execute member(mixcoac, 12). but that doesn't work.

Like this:

?- linea(12, L), member(mixcoac, L).
L = [mixcoac, insurgentes_sur, hospital_20_de_noviembre, zapata, parque_de_los_venados, eje_central, ermita, mexicaltzingo, atlalico|...] ;
false.

This query succeeds once and fails on backtracking. This means that the element mixcoac is seen once in the list of linea(12, L).

The listing I show above is specific to SWI-Prolog, and the fact we are using the toplevel (the interactive shell), and how it is configured by default. This means that other Prologs will look different, and running the code differently will look different. For example, you can use "anonymous variables", starting with underscore, for the list; and you can configure SWI-Prolog's toplevel to not show the bindings for anonymous variables. With nothing else to show, you will get your "true":

?- set_prolog_flag(toplevel_print_anon, false).
true.

?- linea(12, _L), member(mixcoac, _L).
true .

I also typed <kbd>Enter</kbd> instead of <kbd>;</kbd> after the "true". This way I didn't ask for more solutions and I didn't get a "false" ie "there are no more solutions".

All of this under the line is completely irrelevant to your original question.

Also, from your question:

> but i don't know how to work this kind of lists in the Prolog syntax.

This has nothing to do with syntax it feels. Some generic tutorial should have taught you all you need to know.