Question

are these equivalent or not? 2.5(3+x) and 2.5x+7.5 

Answer 1

They are equivalent. 2.5(3+x)+7.5+2.5x. 2.5x+7.5 is the same in opposite order.

Answer 2

$2.5(3+x)=2.5\cdot3+2.5\cdot x=\boxed{7.5+2.5x}$

So, as you can see, 7.5+2.5x = 7.5+2.5x ⇒ 2.5(3+x) and 2.5x+7.5 are equivalent equations.