Simplify the following expression.

(65x+50y) - (16x-21y)

Your going to want to first distribute the negative out to the second equation

65x+50y-16x+21y

49x+71y

81x-29y because you do 65x plus 16x because they both have the variable x at the end. now do 50y plus - 21y and since it is a negetive (and it is a negetive it is not just a subtraction sign trust me i have done this many times before and been correct) you get 29 y because they both have the variable y in it. and you can't do anything with a two different variables.