While the bears were out, goldilocks ate all but 3/8 of papa bear's big green cake off his plate.

then she ate all but 3/8 of the smaller pink cake on baby bear's plate.

whose plate had more cake left on it?

papa bear's plate
baby bear's plate
both plates had the same amount of cake left.

I didn't even draw anything out but I believe that papa bear's plate had more because after all his cake is bigger. 

Theyr basically asking:

does 3/8 of a larger quantity result in a bigger portion left or does than 3/8 of a smaller quantity result in a bigger portion?

let's take papas cake as 24 and the baby's cake as 16. These are just random numbers I chose to show that paps cake was bigger.

so, u have to find out if 3/8 of 24 or 16 is larger.

3/8 of 24 = 8
3/8 of 16 = 6

that means that a fraction of a smaller number will result in a smaller answer.

we cannot really tell if the answer is a or b or c.. but its most likely c because a small portion of a smaller cake is likely to be equal to a large portion of a larger cake.