Answer:
<h3>C. 113°</h3>
Step-by-step explanation:
(7x - 1) + 79° = 21x + 8
• An exterior angle of a triangle is equal to the sum of its two interior opposite angles.

NRS = 21x + 8

Hey there! Your answer us -24° And here you would use subtraction. Hope this helped!! Your fellow Brainly user, GalaxyGamingKitty.