Question

find x
find the measure of the indicated angle.

Explanation:

Step1: Recall angle - sum property of a triangle

The sum of the interior angles of a triangle is 180°.

Step2: Set up an equation

Let the three angles of the triangle be 66°, 78°, and \(x\). Then \(66 + 78+x=180\).

Step3: Simplify the left - hand side

First, add 66 and 78: \(66 + 78=144\). So the equation becomes \(144 + x=180\).

Step4: Solve for \(x\)

Subtract 144 from both sides of the equation: \(x=180 - 144\).
\(x = 36\)

Answer:

36°