Supplementary angles mean that the angles add up to a measure of 180.
angle A+ angle B = 180
(7x+7)+(4x-14)=180
Combine like terms
11x-7=180
11x=187
x=187/11
x=17
Insert x value.
4(17)-14
68-14
54.
Measure of A would be
7(17)+7
126
54+126 is 180 so they are supplementary.
Again, measure of angle B is 54