at first adding and subtracting is all very simple and it all comes around to one common thing among all addition questions, the common denominator.
no question with a different denominator does not work with addition or subtraction, they must have the same.
For our question our common denominator was 15x
so we multiplied the first side by 5 making it 20/15x and the second side by 3 making it 3/15x
adding these is just one step now because of the common denominator
it is 23/15x