The associative property states that we can add numbers in any way we want to still get the same sum, so the parenthesis here can essentially be tossed out to get 3x+2-5=3x-3. However, make sure, for example, that you don't add x and 1 together in 3(x)+1 as you still have to multiply the x with 3 before adding the 1 according to PEMDAS