18+20
Step-by-step explanation:
I'm guessing that "PQPA" means like Problem Question, Problem Answer (so what you are trying to find, and what it is (I think)).
That means the first problem is (3/4)+(7/8) = 13/8 and "How much water is collected in two hours?"
This means the second problem is (2 1/3) - (1 3/4) = (7/3)-(7/4) = 7/12 and "How many pounds of beef are left"
This means the third problem is (1 -(1/6))(2/5) = (5/6)(2/5) = 1/3 and "What fraction of her paycheck is saved"
This means that the fourth problem is (3/4)(2/3) = 1/2 and "How long did it take Megan to do her HW?"