Assume that each ounce of corn puffs provides c calories and each ounce of fruit x provides x calories.

c + 8x = 257

After the substitution, we find that that number of calories that fruit y provides for each ounce is x/(1.8).

c + 8x/(1.8) = 185

Solving both the equations:

8x(8/18) = 72 => x = 81/4 calories

8 ounces of fruit y provides 8(81/4)(10/18) = 20/18 * 81 = 90 calories

Choose C.