Christie has a total of 15 pieces of fruit, all bananas and apples, worth $1.59. Bananas are 13 cents each and apples are 7 cents each. How many bananas and how many apples does she have?

A = apple

b = banana

a + b = 15 so a = 15 - b

0.07a + 0.13b = 1.59

substitute a = 15 - b into 0.07a + 0.13b = 1.59

0.07a + 0.13b = 1.59

0.07 (15 - b) + 0.13b = 1.59

1.05 - 0.07b + 0.13b = 1.59

0.06b = 0.54

b = 0.54/0.06

b = 9

a = 15 - b

a = 15 - 9

a = 6

answer: 6 apples and 9 bananas