Using Equations

The second angle of a triangle is three times the first and the third is 12 degrees less that twice the first. Find numbers for angles.

I do not understand how to solve this equation.

Let A, B and C be angles 1, 2 and 3.

Then, B = 3A and C = 2A - 12

Since the problem states that we are dealing with a triangle, we know that A + B + C = 180º

Substitute for B and C and solve.