The measure of the exterior angle at C is 50 degrees.
This can be found by noting that the exterior angles of a convex polygon always add up to 360 degrees. As a result, we can add each of these angles together and set equal to 360. This will allow us to find x and then find exterior angle C.
(10x) + (4x + 26) + (12x + 44) + (7x - 3) + (6x + 59) = 360
39x + 126 = 360
39x = 234
x = 6
Now that we have the value of x, we can find the value of exterior angle C by plugging in.
C = 4x + 26
C = 4(6) + 26
C = 24 + 26
C = 50