Select the correct answer.
which relation is a function?
a.
{(2, 3), (1, 5), (2, 7)}
b.
{(-1, 5), (-2, 6), (-3, 7)}
c.
{(11, 9), (11, 5), (9, 3)}
d.
{(3, 8), (0, 8), (3, -2)}

↑

↑

↑
arrange the systems of equations that have a single solution in increasing order of the x-values in their solutions.
2x + y = 10
x − 3y = -2
x + 2y = 5
2x + y = 4
5x + y = 33
x = 18 − 4y
y = 13 − 2x
8x + 4y = 52
x + 3y = 5
6x − y = 11
2x + y = 10
-6x − 3y = -2
y = 10 + x
2x + 3y = 45

↑

↑

↑

↑

↑