7 - 5 * (28 - 24)2
First, we take care of the stuff inside parentheses. (28 - 24). Here, we basically have two numbers, the first one is easy, just a 28, the second one is not given in a straight forward manner, rather in terms of an exponent, 2 raised to the power 4. This gives us 16. So far we got (28 - 16). But this is just a subtraction that gives us 12. At this point we are ready to take the parentheses out since we have reduced it to a single number 12:
7 - 5 * 122
We don't have any parentheses left (so we have reduced this from PEMDAS to EMDAS). Next step is to see if we have any E (=exponent), which we do have in 122. This is just 144 and thus, we have:
7 - 5 * 144
So... we have three numbers and two operators. Thus, no exponent (meaning we have reduced it to MDAS). So we do multiplication and division first, before adding or subtracting. Thus, we should do 5*144 before doing the subtraction here:
7 - 720
All we are left with now is a subtraction and subtracting 720 from 7 gives us -713.
Let me know if this makes sense.