Explanation:
The Triangle Sum Theorem states that the interior angles of a triangle add up to 180 degrees. A square for an angle symbolizes that the angle is 90 °, as is the case with angle ∠ACB.
Therefore, as ∠CAB = 2x and ∠ABC = 3x, and angles ∠ACB, ∠CAB, and ∠ABC make up the interior angles of the triangle, we can say that ∠ACB + ∠CAB + ∠ABC = 180, so 90 + 2x + 3x = 180
90 + 2x + 3x = 180
90 + 5x = 180
subtract 90 from both sides to separate the x and its coefficient
5x = 90
divide both sides by 5 to separate the x
x = 18
(a) ∠CAB = 2x = 18(2) = 36
(b) ∠ABC = 3x = 18(3) = 54
(c) Any triangle with a 90° angle is called a right triangle. This has a 90° triangle, and is therefore a right triangle. Similarly, a 90° angle in a triangle is called a right angle.