What's the answer to this?

2 + 3 + 4

Yeah, that's an easy one!

2 + 3 + 4 = 9

What if we grouped the numbers...  Put the 3 and the 4 in parenthesis?  Remember the Order of Operations ...  In math, we always do what's in the parenthesis first!  So, if we do this, will we get the same thing?

2 + ( 3 + 4 ) = 2 + 7 = 9

Yep!

Now, what if we group the numbers differently...  Will we get the same answer again?

( 2 + 3 ) + 4 = 5 + 4 = 9

Remember that, if both things equal 9, then those things have to equal each other!

2 + ( 3 + 4 ) = ( 2 + 3 ) + 4