Answer:
22 cupcakes
Explanation:
First, let's find how many cupcakes he has already made.
He made 13 chocolate and 15 vanilla. If we add them together, we can find how many he has made total.
13+15=28
So far, he has 28 cupcakes.
He needs 50 cupcakes, and he has already made 28. The difference of the two numbers will be how many he must still make.
Subtract 28 from 50
50-28=22
So, he still has to make 22 cupcakes