EXAMPLE
Put x=0, then -y=14, so y=-14 and the ordered pair is (0,-14).
Put y=0, then 7x=14, x=2 and the ordered pair is (2,0).
Put x=y, then 7x-x=14, 6x=14, x=y=14/6=7/3, and the ordered pair is (7/3,7/3).
Put x=1, then 7-y=14, y=-7, and the ordered pair is (1,-7).