I think the answer is 273
You divide 31% by any of the other percentages (like for example, 25%) and then divide 93 by whatever you got as your answer (31 divided by 25 was 1.24, so I divided 93 by 1.24 to get 75) then repeat that with the other percentages and add them all up.
The answer is 7^4/5^2 = 96.04
5 times -7=-35
-10--35=25
25*2=50