Angles are supplement means addition of angles are 180 degree
let's consider
measure of angle = x
measure of supplement angle =x-26
so
x+ (x - 26) = 180
2x -26= 180
2x = 206
x = 103
measure of angle = x=103
measure of supplement angle =x-26=103-26=77
(C) the measure of the angle is 77 degree and the measure of the supplement is 103 degree