What is the measure of the third angle?

Question

In a triangle, the measure of the second angle is twice the measure of the first angle. The third angle is equal to the sum of the other angles. What is the measure of the third angle?

Answer 1

First angle: x

Second angle: 2x

Third angle: x + 2x = 3x

x + 2x + 3x = 180°

6x = 180°
x = 30°

But they ask for the 3rd angle:

3x = 90°

(which makes it a 30°-60°-90° triangle...right?)

Answer 2

The three angles of all triangles sum to 180°.

x = measure of first angle
2x = measure of second angle

Measure of third angle

y = x + 2x = 3x

Sum of all three angles

x + 2x + 3x = 180°
6x = 180°

3x = 180/2 = 90°

The measure of the third angle is 90°.