The key to solving this problem lies in representing the unknowns properly.
Let the first angle be a. Then the second angle, b, is a+20. The third angle is (a+20)+8. Now all of the measurements of angle are in terms of a. Fact: the sum of all the angles of a triangle is 180 degrees.
Thus, a + a+20 + a+20+8 = 180, or:
3a + 48 = 180.
Solve for a by subtracting 48 from both sides: 3a = 132, or a = 44.
The first angle is a = 44 degrees.
The second angle is a+20 degrees, or 64 degrees.
The third angle is a+20+8 degrees, or 72 degrees.
We must check to ensure that these 3 angles do add up to 180 degrees:
44+64+72 = 180