Given: x + y = 15.

Which of the following are ordered pairs of this equation?

{ (-3, 14), (0, 15), (3, 16) }

{ (-3, 16), (0, 15), (3, 14) }

{ (16, - 3), (15, 0), (14, 3) }

For (-3, 14), - 3+14=11, so that isn't right

For (-3, 16), - 3+16=13 so that isn't right

For (16, - 3), 16-3=13 so that isn't right

Do that for everything, and you'll find that the only ones that work are (0,15) and (15, 0) from the ones given