Question

The angles of a triangle are in A.P. whose common difference is 20°. Find the angles.

Answer 1

Let the angles be $$x, x + 20, x + 40$$. 

Their sum is $$180^\circ$$: $$x + (x + 20) + (x + 40) = 180$$. 

So $$3x + 60 = 180$$, giving $$x = 40$$. 

The angles are $$40^\circ, 60^\circ, 80^\circ$$.