1.
The number of degrees in a quadrilateral added up is 360.
The number of degrees in the other angles are 108, 72, and 81.
108+72+81 = 261
To find the last angle, you subtract the number of degrees of the other angles from 360.
360-261 = 99
The measure of unknown angle is 99.
2.
This problem is very similar.
Add up the number of degrees in the other three angles.
95+121+59=275
And you subtract 275 from 360.
360-275 = 85
The measure of the missing angle is 85.