Demetrious returned five library books last week, returned three books this week, then checked out 8 more books. He now has 12 library books. How many books did hehave before last week?

Answer:The number of books that he had before last week is 28

Step-by-step explanation:

Let x represent the number of books that he had before last week.

Demetrious returned five library books last week. This means that the number of books left is x - 5

He returned three books this week. This means that the amount of books left is x - 5 - 3 = x - 8

He then checked out 8 more books. This means that the amount of books left is x-8-8 = x - 16

He now has 12 library books. This means that

x - 16 = 12

x = 12 + 16 = 28