Math

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So I've been working on solving this system by addition/subtraction and I just can't get the right answer. Her is the system of equations I was given to solve by add/sub:

3x – y = –12
x + 2y = –18

• Math -

double the first:
6x - 2y = -24
x + 2y = -18
7x = -42
x = -6

back into the second:
-6 + 2y = -18
2y = -12
y = -6

x = -6 , y = -6

• Math -

solve the system by substitution
6x+2y=-18
-x+5y=19

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