Question 476438
Given:
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10y = 5y + 9 + 4y
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To solve this, begin by collecting all the terms that contain y on one side of the equation and thereby leaving everything else on the other side of the equation. Normally you collect the terms containing an unknown variable, in this case containing a y, on the left side.
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To move the 5y to the left side, subtract 5y from both sides.  
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10y - 5y = 5y - 5y + 9 + 4y
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On the left side the 10y and -5y combine to give +5y and on the right side the 5y and the -5y cancel each other, so the 5y on the right side disappears.  This leaves:
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5y = 9 + 4y
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Next, to get rid of the 4y on the right side, subtract 4y from both sides. This results in:
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5y - 4y = 9 + 4y - 4y
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On the left side the 5y - 4y combine to give just y. And on the right side the 4y and -4y cancel each other and disappear.  Therefore, you are left with:
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y = 9
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That is the answer for what value of y will make the equation OK.
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You can check this answer by going back to the original equation of the problem and substituting 9 in place of y.  When you do that the left side of the equation should equal the right side. Here we go:
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10y = 5y + 9 + 4y
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Substitute 9 for y and you have:
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10*9 = 5*9 + 9 + 4*9
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90 = 45 + 9 + 36
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90 = 54 + 36
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90 = 90
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Both sides are equal, and therefore, when y = 9 the equation balances. This tells you that the answer is correct and y = 9.
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Hope this helps you to understand algebra a little better.