Which sets of ordered pairs represent relations that are functions? you may choose more than one correct answer,
((1), (2.0), (3, 0), (4,0))
(2,3), (2, 4), (2,5), (2,6)}
((11), (2, 2), (3, 3), (4,4))
{(1,3), (-1,4), (1,4), (-1,3)
(6,6), (-6, 6), (5-5), (-5,5))

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.