Hey!!
We know, a straight line has an angle of 180 degrees
A triangle has 3 straight lines
We are given two exterior angles , Now let us find the supplementary angle, which is the angles which completes a straight line with the given angles
1st angle = 150
supplement = 180 - 150
= 30
One angle of a triangle is 30
2nd angle = 120
supplement = 180 - 120
= 60
The second angle is 60 degrees
Ina triangle, if we add up all the angles , we get 180. This is called the interior angle property of a triangle
we got, 30 , 60 and we got to find one more
let us take the third angle as ' x '
30 + 60 + x = 180
90 + x = 180
x = 90
The angles of a triangle are
30 , 60 , 90
Hope helps!