Question

Mike and Bill sell cars for Jangle's Auto. Over the past year they sold 640 cars. Assuming Mike sells 3 times as many as Bill, how many cars did Mike sell?

Answer 1

M+B=640

M=3B

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Therefore:

3B+B=640

4B=640

B=640/4=160

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M+160=640

M=640-160=480

Therefore, Mike had sold 480 cars.

Answer 2

Over the past year they sold 640 cars. Assuming Mike sells 3 times as many as Bill:

x --> cars sold (by Mike)
y --> cars sold (by Bill)

x + y = 640
x = 3y

3y + y = 640
4y = 640 |:4
y = 160

x = 3y = 3 * 160 = 480

Mike sold 480 cars and Bill sold 160 cars.