In a package of 25 colored pencils 8 are red , if you bought 125 pencils how many would be red

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

a negative exponent is translated as follows:

so, we have