# Homework help for math. Needed to help son.?

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y = pencils

4x + 9y =$8.90

2x + 6y = $5.20 Multiply this equation by -2 so we can eliminate one variable

4x + 9y = $8.90

-4x – 12y = – $10.40 The 4x cancels out.

-3y = -$1.50 Divide by -3

y = $.50 for each pencil

Now substitute for y to solve for x.

4x + 9($.50) = $8.90

4x + $4.50 = $8.90

4x = $4.40

x = $1.10 for each pen

To check substitute the values in each equation and it will work.

4x + 9y = 890

2x + 6y = 520 (in cents)

This is how, algebraically. Other ways include guess and check- just guess some prices that work for one equation and see if they work for the other; if not change them until they do. Not very efficient unless you are a lucky guesser though.

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