1) Let's use the Elmination Method:
x - 2y = 10 x -3 To eliminate 'x' when adding both
3x + y = -12
-3x +6y = -30
3x + y = -12
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0 7y = -42 Divide both sides by 7
y= -6
2) Let's plug into the simpler equation the value for y
x - 2y =10
x +12 = 10 subtract 12 from both sides
x = -2
3) So, the solution to that system is S = (-2, -6)
