The angle A of the parallelogram is 3 times less than the angle B, find the angle D?

1. Let’s denote the degree measure of the angle A through x.

2. Determine the degree measure of the angle B:

3 * x = 3x.

3. Let’s compose and solve the equation:

3x + x = 180˚;

4x = 180˚;

x = 180˚: 4;

x = 45˚.

4. The degree measure of the angle A is equal to 45˚.

5. What is the degree measure of angle B?

3 * 45˚ = 135˚.

6. What is the angle D equal to?

Since angle B is equal to angle D, then the degree measure of angle D is 135˚.

Answer: angle D is 135˚.