What is the value of r? (5, 2), (-7, r), m = 5/6

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

the answer is simply just 6n add the two together as they have an n