A rabbit on a controlled diet is fed daily 300 grams of a mixture of two foods, food X and food Y. Food X contains 10% protein and food Y contains 15% protein. If the rabbit's diet provides exactly 40 grams of protein daily, how many grams of food X are in the mixture. Choose the correct answer:
A) 100
B) 140
C) 150
D) 160
E) 200
Let x be the amount of food X.   0.1x + 0.15(300-x) = 40   0.05x = 5   x = 100   The answer is 100.
<result>A</result>
A rabbit on a controlled diet is fed daily 300 grams of a mixture of two foods, food X and food Y. Food X contains 10% protein and food Y contains 15% protein. If the rabbit's diet provides exactly 40 grams of protein daily, how many grams of food X are in the mixture.