Question 535652: I honestly have no idea what toopic this question would fall under... Solve this system of equations using substitution. Put your answer in ordered pair form, (x, y). x + 2y = 7 and 2x + y = 8 I can't figure out how to do it. I've tried to many times, but I can't figure it out. Can you please help me?
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! Solve this system of equations using substitution. Put your answer in ordered pair form, (x, y).
x + 2y = 7
2x + y = 8
we can use the 2nd equation for substitution
2x + y = 8
Subtract 2x from both sides
y = -2x + 8
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Now we can substitute (-2x+8) for y in the 1st equation
x + 2y = 7
x + 2(-2x+8) = 7
x - 4x + 16 = 7
subtract 16 from both sides
x - 4x = 7 - 16
do the math
-3x = -9
x has to be positive, multiply both sides by -1, this changes the signs
3x = 9
divide both sides by 3
x = 9/3
x = 3
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We can use the equation y =-2x+8, to find y, replace x with 3
y = -2(3) + 8
y = -6 + 8
y = 2
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the x,y form (3,2)
:
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Check our solutions in the 1st equation
x + 2y = 7
replace x and y with our solutions
3 + 2(2) = 7
3 + 4 = 7, confirms our solution
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Are you understanding this better now, any questions?
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