Lucy bought 7 fiction books of the same kind during the Grand Opening Sale. Gillian bought 5 of the same fiction books. Gillian also bought 2 buttons at $2.70 each. Altogether, she spent $1.60 more than Lucy. What was the amount Gillian spent?
Amount that Gillian spent on 2 buttons
= 2 x 2.70
= $5.40

Let the cost of each fiction book be 1 u. 

Amount that Lucy spent = 7 u

Amount that Gillian spent =  5 u + 5.40

Gillian spent $1.60 more than Lucy.  If Lucy spent another $1.60, she would spend the same amount as Gillian.

7 u + 1.60 = 5 u + 5.40
7 u - 5 u = 5.40 - 1.60
2 u = 3.80

1 u = 3.80 ÷ 2 = 1.90

Cost of each fiction book
= 1 u
= $1.90

Amount that Gillian spent
= 5 x 1.90 + 5.40
= 9.50 + 5.40
= $14.90

Answer(s): $14.90