How to make a text bold in helper.rb ruby file inside a string

i have one mailer file called schedule_mailer.html.erb
in that I'm trying to use a helper method from that I'm rendering the contents

in scheudle_mailer.html.erb

<p style='font-size:15px;margin:0 25px 20px 25px' >
  <%= body_text_tag() %>
</p>

in helper.rb
i need to send a string which includes <b> as well as <br>
but I'm receiving in mail as <b> and <br> tag itself.

my helper method

def body_text_tag()
      body = "This email to inform you that"
        if @creation 
          body +  "your hotel schedule has been created <br>
          <b>timings :</b>  #{@timings}, <br>
          <b>Room number :</b> #{@room number},<br>
          ....
          ....
          ....
        elsif ....
       .....
end.

as I have tried tag(:br), inside the string, even though it's rendering the mail with the tag(:br) itself, instead of the break line.
how to approach this kind of tags in the string to HTML?

The reason this doesn't work is that in Rails when you append a normal string to a safe buffer its automatically escaped to prevent XSS attacks.

irb(main):076:0> "<b>Hello".html_safe + "World</b>"
=> "<b>HelloWorld</b>"

If you want to create text that contains HTML tags from a helper you need to mark the portions that are HTML tags as safe:

"<b>".html_safe + @timings + "</b>".html_safe

Do not do:

"<b>#{ @timings }</b>".html_safe 

Unless you actually know that the content is actually safe and doesn't contain user input.

This is what the tag helpers do automatically for you:

content_tag(:b, @timings)
tag.b(@timings) 

But this code most likely doesn't actually belong in a helper in the first place. Use a view or a partial and write it in ERB.

one of the solutions which I tried and worked for me is to use html_safe, in the mailer.
as
<%= body_text_tag().html_safe %>