Question 70698
Your answer is incorrect.  Maybe I can help you to find your error. Let's begin by simplifying 
the two equations a little.
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The first equation is {{{2x + y = 3x - 15}}}. You have two terms that contain x.  Let's move
the x from the right side by adding -3x to it.  This cancels the +3x on the right side.  However,
if you add -3x to the right side, you must also add -3x to the left side.  When you do that
you add the -3x to the +2x that is already on the left side.  The result is -x.  So the first
equation is reduced to:
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{{{-x + y = -15}}}
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That's a little easier to work with.  Now let's go to work on the second equation:
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{{{x+5=4y+2x}}}
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Notice the right side has only terms with variables. Let's move them to the left side so
the equation has all the terms containing x and y on the left side just like the first
equation does. Let's first add -2x to both sides.  On the right side the -2x cancels
the +2x so the +2x disappears. And on the left side you add the -2x to the +x to get the
sum of -x.  Now add -4y to the right side term of +4x.  When you do the 4x is canceled and
you are left with zero on the right side. There is no y term on the left side so when we
add -4y that term appears on the left side unchanged. At this point the second equation is:
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{{{-x - 4y + 5 = 0}}}
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Notice now that the +5 should be on the right side instead of the left side.  Move this
term to the right side by adding -5 to both sides.  The -5 adds to the +5 on the left side
and it cancels it out.  On the right side when we add -5 to 0 the result is -5. So finally 
we are at the point of knowing that the second equation is:
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{{{-x - 4y = -5}}}
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Now we are at the point of saying that our set of two equations has been changed to:
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{{{-x + y = -15}}}
{{{-x - 4y = -5}}}
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To eliminate the x term we can subtract the second equation from the first equation. 
(If you prefer you can think of multiplying the entire second equation by -1 and then adding 
it to the first equation.) As a result of this subtraction, the x terms disappear.
The y term of the answer is 5y and the numbers on the right side subtract to give an
answer of -10.  We are left with:
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{{{5y = -10}}}
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which we can solve by dividing both sides by 5 to get {{{y = -2}}}
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Now knowing that y = -2, we can return to either of the original equations and substitute
-2 for y. Then we can solve for x.  Let's return to the original first equation of:
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{{{2x + y = 3x - 15}}}
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When we substitute -2 for y in this equation, the equation becomes:
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{{{2x - 2 = 3x - 15}}}
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Then we can add +2 to both sides. Following that we add -3x to both sides. Do you see why?
The resulting equation is:
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{{{-x = -13}}}
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Since we are to solve for +x, we can do so by multiplying both sides by -1 to get:
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{{{x = 13}}}
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In summary the answers are {{{x=13}}} and {{{y=-2}}}
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Hopefully this will help you to understand the problem and to track down your errors.