Question 110583
The 3 outside the parentheses tells you to multiply each of the terms inside the parentheses by 3.
Do this first.
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3 times 7 is 21 and 3 times -2y is -6y. So the left side is multiplied out and the equation becomes:
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21 - 6y = 9
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Next your goal is to get all the terms with y on one side of the equation and all the numbers 
on the other side.
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Note that if you subtract 21 from the left side the 21 will go away. But if you subtract 21
from the left side you must also subtract 21 from the right side. The first step is to subtract
21 from both sides. When you do you get:
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21 - 6y - 21 = 9 - 21
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On the left side 21 minus 21 is zero. On the right side 9 - 21 = -12. These two subtractions
reduce the equation to:
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-6y = -12
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Finally you can solve for y by dividing both sides of the equation by -6 which is the 
multiplier of y. This division leads to:
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{{{(-6y)/-6 = (-12)/(-6)}}}
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On the left side the -6 in the numerator cancels the -6 in the denominator and you are left
with just y. On the right side the division of -12 in the numerator by -6 in the denominator
results in +2. So you are left with:
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y = 2
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This should be the answer. You can check it out by returning to the original problem,
substituting 2 for y, and making sure that the left side of the equation is equal to the
right side.
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So start with the original equation:
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3*(7 - 2y) = 9
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Put 2 in for y to make this equation become:
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3*(7 - 2*2) = 9
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Inside the parentheses multiply the 2*2 to get 4. Put 4 in place of 2*2 and the equation 
becomes:
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3*(7 - 4) = 9
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The number inside the parentheses is 7 - 4 which is 3. So replace 7 - 4 with 3:
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3*(3) = 9
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and on the left side the 3 times 3 is equal to 9 and therefore the left side is 9 and
the equation becomes:
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9 = 9
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Your answer of y = 2 is correct because when 2 is substituted for y in the original 
problem, the left side of the equation is equal to the right side.
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Hope this helps you to see how to work this problem.
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