Problem Solving

The entire contents of a full sack of flour can be used to make 15 cupcakes and 8 pizzas. The same full sack of flour can be used to make 7 cupcakes and 14 pizzas. If a full sack of flour is used to make only pizzas, how many pizzas can be made?

18.25
18.5
18.75
19
19.25

Another good one from magoosh.com, so sharing again.
OA is E

C flour is used to make each cupcake and P flour is used to make each pizza. Therefore:

15C+8P=7C+14P

8C=6P

C=3P/4

Substitute C=3P/4 into any of the two expressions given in the problem to come up with an answer of how many pizzas can be made with a full sack of flour.

Let's use the first expression:

15(3P/4)+8P=77P/4=19.25P

19.25 pizzas can be made with a full sack of flour.