Question

Can you please help me with the subtraction

Answer 1

For this equation, all are subtraction symbols which means you don't need to care about the parenthesis as they do nothing. 

Basically, it's the associative property because the parenthesis do nothing to the equation and both sides stay the same

Answer 2

You subtract what is in the parentheses first so it would be 9-3 = 15-3 which is not true. So the equation is nonsense and the associative property doesn't work with subtraction.