Hi, so I was wondering what the first part of the equation could be? I thought it would just be 10i

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

my guess would be b and d, but i didn’t actually get out the pen and paper. lol