The problem we are asked to simplify is:
(3x + 4y = 17) - (3x + 2y = 3)
To subtract the equations, we do what we would normally do, combine like terms. This gives us our answer equation of:
(3x - 3x) + (4y - 2y) = (17 - 3)
This gives us our answer of:
2y = 14
But, if we would want to solve it (the question doesn't ask us for this), we find that y = 7 and substitute the value of y in one of the equations to find x.