To solve this question, we are going to follow the steps below:
First you need to know that two angles are said to be supplemenatary when they sum up to 180°
On the note
Since ZA and ZB are both supplementary
It means
ZA + ZA = 180 -----------------------------------(1)
But
ZA = 6x + 3 and ZB = 8x - 5
substituting the above in equation (1)
(6x+3) + (8x-5) = 180
6x+3+8x - 5 = 180
6x+8x +3 -5 = 180
14x - 2 = 180
Add 2 to both-side of the equation
14x -2 + 2 = 180 + 2
14x = 182
Divide both-side of the equation by 14
x =13
MZA = 6x+3 ( substitute x=13)
MZA = 6(13)+3 =78 + 3 = 81
Similarly
mZB = 8x - 5 (substitute x=13)
mZB = 8(13) - 5 = 104- 5 = 99