Question

I will mark BRAINLIEST for the right and well explained answer!

Answer 1

The three interior angles of any triangle add to 180 degress.  Therefore,

180-(120 + 40) = the third angle.

So, 20 is the third angle

Answer 2

Answer: 20°

Step-by-step explanation:

1. B = 120°, C = 40°             1. Given

2. A + B + C = 180°             2. Triangle Sum Theorem

3. A + 120° + 40° = 180°      3. Substitution Property

4. A + 160° = 180°                4. Simplify (added like terms)

5. A = 20°                            5. Subtraction Property of Equality