According to PEMDAS, you would look in the parenthesis first. In the first set of parenthesis we have an exponent. 10x10x10x10 is 10,000. Then we multiply this by 2.5. We now have 25,000. We put this to the side..
Next, we do the same thing on the other side -- 10x10x10 is 1,000 and then you multiply that answer by 1.5 and we have 1,500. Now we can subtract. 25,000 - 1500 = 23,500 :)