In triangle ABC, angle B is a straight line, and angle C is 30 degrees less than angle A.

From the condition we know that in triangle ABC the angle B is equal to 90 °, and the angle C is 30 ° less than the angle A.

In order to find the degree measure of the angles C and A, we compose and solve a linear equation.

We denote by the variable x the degree measure of the angle A, then the degree measure of the angle C is equal to (x – 30).

From the theorem on the sum of the angles of a triangle, we know that the sum of the angles of a triangle is 180 °.

Let’s compose and solve the equation:

90 + x + x – 30 = 180;

2x = 180 – 90 + 30;

2x = 120;

x = 120: 2;

x = 60 ° angle A, then the degree measure of angle C is 60 – 30 = 30 °.