Question 9271
You need to know that the sum of all the angles in a triangle = 180.

so in your problem:

you can write your problem 2a + a + 5a = 180

combining the "a" we get 8a=180

divide out the 8 on both sideS:  a = 180 / 8

a = 22.50

answer:

the second angle  = 22.50

The first angle = 2 x 22.50 = 45.0

The third angle = 5 x 22.50 = 112.50

to check, add all the angles AND THEY MUST EQUAL 180 = 22.50 + 45.0 + 112.50 = 180.