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 Post subject: Book 2 Question 58 Page 74Posted: Sun Dec 04, 2011 11:18 am

Joined: Fri Mar 18, 2011 12:27 pm
Posts: 17
I understand how the equations are set up but I can't seem to solve them.
Can you please walk me through the steps?

Thank you!

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 Post subject: Re: Book 2 Question 58 Page 74Posted: Mon Dec 05, 2011 8:37 pm

Joined: Thu Feb 12, 2009 6:32 pm
Posts: 497
If you understand how the equations are set up, then you've gotten through the hardest part. Here are the rest of the steps:

5x/7x = original ratio
3y/2y = new ratio

5x + 3 = 3y
7x - 9 = 2y

I'd try to combine these two equations.
If we multiply 5x + 3 = 3y by 2, we have 6y on the right, and
if we multiply 7x - 9 = 2y by 3, we have 6y on the right.

Our two equations are now:
10x + 6 = 6y
21x - 27 = 6y

Since both are equal to 6y, we can set them equal to each other:
10x + 6 = 21x - 27
33 = 11x
3 = x

We can then plug x=3 back into either equation to find y:
5x + 3 = 3y
5(3) + 3 = 3y
15 + 3 = 3y
18 = 3y
6 = y

Therefore, the number of red pens after the change is 2y, which is 2*6, or 12.

Veritas Help

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 Post subject: Re: Book 2 Question 58 Page 74Posted: Tue Dec 06, 2011 5:30 pm

Joined: Fri Mar 18, 2011 12:27 pm
Posts: 17
Thank you very much!

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