3x-y=7 2x+y=8

3x - y = 7             (1)

2x + y = 8            (2)

Add (1) and (2) term by term to eliminate y

5x = 15

Divide both sides by 5

x = 3

Put this back into (2)

2*3 + y = 8   or   6 + y = 8

Subtract 6 from both sides

y = 8 - 6  or  y = 2

You should check these by putting them back into the original equations to see if the left-hand sides equal the right-hand sides.

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