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 Post subject: Math Essentials Q5 p.91Posted: Thu Dec 02, 2010 9:05 pm

Joined: Tue Nov 16, 2010 5:56 pm
Posts: 5
Q5. Solve for x and y
1) 2y - 3x = 12
2) y + 2x = 10

In this question, we determine the value of x by substituting y = 10 - 2x into the first equation, which gives us x = 8/7.

When we calculate the value of y by substituting x = 8/7 in the second equation, we are left with y + 16/7 = 10. The answer shows a value for y of 54/7 which can only be derived by substracting 16/7 from both sides.

I don't understand why we can't multiply both sides by 7, then substract 16 from both sides, which would give y = 54. Can you please explain?

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 Post subject: Re: Math Essentials Q5 p.91Posted: Sun Dec 05, 2010 7:40 pm

Joined: Thu Feb 12, 2009 6:32 pm
Posts: 497
Starting here:
y + 16/7 = 10
We can absolutely multiply both sides by 7:
7y + 16 = 70
7y = 54
y = 54/7

We just have to remember to multiply everything on the left side of the equation by 7 instead of just the second term.

Veritas Help

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