Question

adam spent 13.10 on supplies for school. book covers cost 1.50 and boxes of mechanical pencils were each 2.80. if he bought seven items total, then how many of each did he buy

Answer 1

5 book covers and 2 boxes of pencils

Explanation:

If all 7 were book covers, the cost would be 10.50. The cost is 2.60 more than that. Each box of mechanical pencils costs 1.30 more than a book cover, so there must be 2.60/1.30 = 2 boxes of mechanical pencils (and 5 book covers).

_____

If you want an equation, let p represent the number of pencil boxes. Then 7-p is the number of book covers.

... 1.50(7-p) +2.80p = 13.10

... 1.30p = 13.10 -10.50 . . . . . subtract 10.50, collect terms

... p = 2.60/1.30 = 2 . . . . pencil boxes

... 7-2 = 5 . . . . . book covers