At a shop, Luke paid $12 for 1 story book and 3 textbooks. The story book cost $3 more than the total cost of all the textbooks.
- How much did 1 story book cost?
- How much did 1 textbook cost?
(a)
Cost of 3 textbooks = 1 u
Cost of 1 story book = 1 u + 3
Total cost of 3 textbooks and 1 story book
= 1 u + 1 u + 3
= 2 u + 3
2 u + 3 = 12
2 u = 12 - 3
2 u = 9
1 u = 9 ÷ 2 = 4.50
Cost of 1 story book
= 1 u + 3
= 4.50 + 3
= $7.50
(b)
Cost of 3 textbooks = $4.50
Cost of 1 textbook
= 4.50 ÷ 3
= $1.50
Answer(s): (a) $7.50; (b) $1.50