P.E.M.D.A.S
First , you multiply.
200+(-16)4
200+(-64)
Since they have different signs, you subtract and keep the sign of the greater absolute value.
200+(-64)=136
3/4 divided by 8 can be done by doing 3/4 times 1/8 (which is the reciprocal of 8). When multiplied through, your answer should be 3/32. It cannot be simplified any further, so each student will get 3/32 of the cake. Hope this helps :)