9514 1404 393
Answer:
Step-by-step explanation:
The sum of the two adjacent angles is equal to the angle that includes both.
∠NBS +∠SBR = ∠NBR . . . . . angle sum theorem
(12x -4) +42 = (17x +8)
30 = 5x . . . . . . . . . . . . . . subtract 12x+8
6 = x . . . . . . . . divide by 5
__
Then the measure of ∠NBS is ...
∠NBS = 12x -4 = 12·6 -4
∠NBS = 68 . . . . degrees
