Gavin needs to buy candy for the 11 students in his class plus himself. Gavin and each student will get one bag of candy. He uses $ 20 to buy two different types of candy. Gavin buys x bags of gummy bears that cost $ 1.50 per bag and y bags of chocolates that cost $ 2.00 per bag. The system of equations used to represent this situation is graphed, as shown. How many bags of gummy bears does Gavin buy?