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Answer:
(b) 108°
Explanation:
Consecutive interior angles are supplementary, so we have ...
R + S = 180°
(3x +12)° +(5x +8)° = 180°
8x +20 = 180 . . . . . . . . . . . . divide by °, collect terms
8x = 160 . . . . . . . . . . . . . subtract 20
x = 20 . . . . . . . . . . . . divide by 8
Then the measure of angle S is ...
S = (5x +8)° = (5·20 +8)°
S = 108°