If B is a complement of A this means that the sum of the measures of A and B is 90 degrees.
mA + mB = 90
mB =90 - mA
mB = 90 - 40 = 50
Thus, the measure of angle B is 50 degrees.
If C is a supplement of B then, the sum of the measures of B and C is 180 degrees.
mC + mB = 180
mC = 180 - mB
mC = 180 - 50 = 130
Therefore, the measure of angle C is 130 degrees.