Question
Evan washes two types of vehicles. It takes him 30 minutes to wash a car and 40 minutes to wash a truck. He charges $12 to wash a car and $15 to wash a truck. In 270 minutes, Evan made $105 washing cars and trucks. How many trucks did Evan wash?
Answers
30c+40t = 270
12c+15t = 105
now, from the 2nd equation we see that
12c = 105 - 15t, so
30c = 5/2 (105-15t)
plugging that into the 1st equation, we get
5/2(105-15t) + 40t = 270
5(105-15t) + 80t = 540
105-15t+16t=108
t = 3
12c+15t = 105
now, from the 2nd equation we see that
12c = 105 - 15t, so
30c = 5/2 (105-15t)
plugging that into the 1st equation, we get
5/2(105-15t) + 40t = 270
5(105-15t) + 80t = 540
105-15t+16t=108
t = 3
t=3
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