Can someone

use elimination to solve for x and y:

−2x−y=9

2x−9y=1

my choices

a. (−4,−1)
b. (−1,−4)
c. (5,1)
d. (−1,−7)

the sum of all the angles in a triangle are equal to 180

so you can add   the 3 given angles together to equal 180:

5y + 2y + 2y = 180

or since all three angles have the same letter, combine the 3 angles to equal 180:

9y = 180