Answer:
[tex]\boxed {\boxed {\sf m \angle 1 = 68 \textdegree}}[/tex]
Step-by-step explanation:
The 3 interior angles of a triangle must add to 180 degrees.
We don't know the measure of angle 1. We can say the measure of angle 2 is 61° and the measure of angle 3 is 51°.
Add the numbers on the left side.
We want to isolate the measure of angle 1.
112 is being added, so we must perform the inverse operation of subtraction.
- m∠1 +112°-112°= 180°-112°
- m∠1= 180° - 112°
- m∠1=68°
The measure of angle 1 is 68 degrees.
