The total number of cars both the student and the teacher made is 49
let
total cars = x
cars made by student = s
cars made by teacher = t
Total = student + teacher
x = s + t
s = 2/7x
So,
x = 2/7x + t
x - 2/7x = t
t = (7x - 2x) / 7
t = 5/7x
Similarly,
s = t - 21
s = 5/7x - 21
equate both s equation
2/7x = 5/7x - 21
2/7x - 5/7x = -21
(2x - 5x) / 7 = -21
- 3/7x = -21
x = -21 ÷ -3/7
= -21 × - 7/3
= (-21 × -7) / 3
= 147/3
x = 49
Therefore, the total number of cars both the student and the teacher made is 49
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