SASS/SCSS Avoid duplicate properties including two mixins or extending two classes

Let's say that I have two classes that I can @extend (or two mixins I can @include) like so:

.small-text {
    font-family: "MyFontFamily";
    color: black;
    line-height: 1rem;
    font-size: 1rem;
}
.large-text {
    font-family: "MyFontFamily";
    color: black;
    line-height: 1.4rem;
    font-size: 1.4rem;
}

Now, all throughout my SCSS, I can do things like this:

h1 {
    @extend .large-text;
}
h3 {
    @extend .small-text;
}

But now let's say that I want to use a class name, or a media query, to selective change from small to large text:

h3 {
    @extend .small-text;
    
    &.big {
        @extend .large-text;
    }
}

The problem I'm having is the the compiled CSS is going to be really duplicative, like so:

h3 {
    font-family: "MyFontFamily";
    color: black;
    line-height: 1rem;
    font-size: 1rem;
}
h3.big {
    font-family: "MyFontFamily";
    color: black;
    line-height: 1.4rem;
    font-size: 1.4rem;
}

Is there any way to only include the changed properties in the second selector which changed from the first selector?

Nothing has duplicated, that is exactly what you asked for, what you should do instead is have a another class that both small-text and large-text both use called text

So it would be like this

.text { 
    font-family: "MyFontFamily"; 
    color: black; 
} 
.small-text { 
    line-height: 1rem; 
    font-size: 1rem; 
}
h3 {
    @extend .text;
    @extend .small-text;
    
    &.big {
        @extend .large-text;
    }
}

So when you extend from the small and large classes it will only include the line-height and font-size