Answer:
We can find the sum of the interior angles of any polygon using the formula
, where n is the number of sides.
Because each of these polygons have four sides, we can use one formula where our n is 4 to find the sum of the interior angles:

Thus, for all four problems, we can set the four angles equal in the four polygons equal to 360 and solve for the variables
(15) *Note the right angle symbol in this problem which always equals 90°

Now, to find the measure of <Y, we simply plug in 0 for x in its equation
m<Y = 2(0) + 118 = 118°
(16):

To find the measure of <F, we plug in 9 for x in its equation
m<F = 10(9) = 90°
(17):

To find the measure of <M, we plug in 9 for x in its equation
m<M = 10(9) - 5 = 85°
(18):

To find the measure of <M, we plug in 8 for x in its equation
m<M = 11(8) - 2 = 86°