Question

find the measure of the missing angle.

Explanation:

Step1: Identify right angle

The triangle has a right angle ($90^\circ$).

Step2: Sum of triangle angles

Triangle angles sum to $180^\circ$. Let missing angle be $x$.
$$20^\circ + 90^\circ + x = 180^\circ$$

Step3: Calculate missing angle

$$x = 180^\circ - 20^\circ - 90^\circ = 70^\circ$$

Answer:

$70^\circ$