What’s the missing angle

A) 150

Step-by-step explanation:

All the angles in a triangle must add up to a total of 180 degrees.

So we can make an equation as given below:

20+10+?=180

30+?=180

?=150

So the missing angle is 150 degrees

150

Step-by-step explanation:

Subtract 20 and 10 to 180 because the side of a triangle(or all three sided figures) is 180 and you get 150