a)
Lets p = # of fruit pies sold and j = # of bottles of fruit juice sold
Together both classes sold 79 items: p + j = 79
Fruit pie sold sold $1.65 each and bottle of fruit juice sold $1.36 each and together earned $118.17 = 1.65p + 1.36j = 118.17
Now you have two equations
p + j = 79 --> p = 79 - j
1.65p + 1.36j = 118.17
Substitute p = 79 - j into 1.65p + 1.36j = 118.17
1.65(79 - j) + 1.36j = 118.17
130.35 - 1.65j + 1.36j = 118.17
- 0.29j = - 12.18
j = 42
Substitue j = 42 into p = 79 - j
p = 79 - j = 79 - 42 = 37
# of fruit pies sold = 42 and # of bottles of fruit juice sold = 37
b)
Mr. Sanchez's class : $1.65 (37) = $61.05
Mr. Kelly's class: $1.36 (42) = $57.12
Mr. Sanchez's class sold more money than Mr. Kelly's class.
c)
$61.05 - $57.12 = $3.93
Mr. Sanchez's class earned $3.93 more than Mr. Kelly's class