Economics - Absolute Prices

Let x be the unit price of protein in cents per gram.
Let y be the unit price of carbs in cents per gram.

The info you have translates to:
600 = 12x + 6y
500 = 5x + 15y

Solve for x and y.

(Note: I am assuming here that the food item price is purely a linear function of grams of protein and grams of carbohydrate. In real life, that assumption is nonsense.)

Boy, I'll say. Carbohydrates are notoriously scarce in meat - except for glycogen stored in the liver.