At first, Joe had $177 and Calvin had $129. Each of them bought a pair of jeans and a shirt. The pair of jeans cost 3 times as much money as the shirt. In the end, Joe had 3 times as much money as Calvin. What was the cost of the pair of jeans?
Initial money Joe had = $177
Initial money Calvin had = $129
Let the cost of jeans = x
Let the cost of a shirt = y
Pair of jeans cost 3 times as the shirt
=> x = 3y — 1
Money remaining with Joe = Initial money - cost of jeans - cost of shirt = $177 - x - y
Money remaining with Calvin = Initial money - cost of shirt - cost of jeans = $129 - x - y
It is given remaining money of Joe is 3 times the money remaining with Calvin.
=> ($177 - x - y) = 3($129 - x - y)
=> $177 - x - y = $387 - 3x - 3y
=> -x - y + 3x + 3y = $387 - $177
=> 2x + 2y = $210
Use equation 1 =
2(3y) + 2y = $210 => 6y + 2y = $210
=> 8y = $210 => y = 210/8
=> y = $26.25
Substitute back in 1:- x = 3($26.25)
=> Cost of pair of jeans = $78.75