Answer:
Let P represent the number of pies sold and J represent the number of juices sold. 
 
a) 
 
The first equation for the sum of the sales: 
 
P + J = 79 
 
P = 79 - J 
 
Next, for the sum of the amounts earned: 
 
1.65P + 1.36J = 118.17 
 
Substituting P, 
 
1.65 (79 - J) + 1.36J = 118.17 
 
J = 42 
 
Using this value of J, 
 
P = 79 - 42 
 
P = 37 
 
b) 
 
Mr. Sanchez's class earned: 1.65 x 37 = $61.05 
 
Mr. Kelly's class earned: 1.36 x 42 = $57.12 
 
So Mr. Sanchez's class earned more money. 
 
c) Mr. Sanchez's class earned: 
 
61.05 - 57.12 
 
= $3.93 more than Mr. Kelly's class
Explanation:
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