Ok so for the first one:
-We know that the 4 angles add up to 360
-3 of the angles are given
-To find the fourth we simply subtract the sum of the 3 angles from 360.
Equation: 120+ 100+ 100 + x = 360
= 320+x= 360
Now by making x the subject
x= 360 - 320
= 40 degrees
The second one follows the same method
150+ 77+ 48+ x =360
275 +x = 360
x= 360-275
x= 85