Answer: : x = 4 and y = -2.
5x + 4y = 12 /*3
3x - 3y = 18 /*4
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15x + 12y = 36
12x - 12y = 72
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15x + 12y + 12x - 12y = 36 + 72
15x + 12x = 36 + 72
27x = 108
x = 108/27
x = 4
3x - 3y = 18
3 * 4 - 3y = 18
12 - 3y = 18
12 - 18 = 3y
3y = -6
y = -6/3
y = -2
