Question

Kate had twice the number of toy bricks as Jake. Jake used all his bricks to build 5 identical cars. Kate used all her bricks to build 7 identical cars. Kate used 9 more bricks than Jake for each car. How many bricks did Kate have?

Answer 1

Jake's number of bricks --- 5x

Kate's number of bricks ---- 7y
7y = 2(5x)
7y = 10x
y = 10x/7 , #1

Jake's bricks per car = x
Kate's bricks per car = y
y = x + 9 , #2

substitute #2 into #1:
x+9 = 10x/7
7x + 63 = 10x
3x = 63
x = 21 , then y = 30 , now you can find all about the problem

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