Answer:
The mistake was made in the second step when going from 3x - 2(3x-4) = 13 to 3x - 6x - 8 = 13.
The mistake was in the multiplication of -2(3x-4). The error is that the negative sign was not distributed to both the 3x and the -4.
-2 times 3x is -6x and -2 times -4 is positive 8
Explanation:
y = 3x - 4
3x - 2y = 13
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3x - 2(3x - 4) = 13
3x - 6x + 8 = 13
-3x + 8 = 13
-3x = 5
x = -5/3
y = 3(-5/3) - 4
y = -5 - 4
y = -9
Solution: x = -5/3 and y = -9