Answer:
27
Explanation:
15x-31 = 9x+11
6x-31 = 11
6x = 42
x = 7
15x -31 + 9x + 11 + s = 180
15(7) -31 + 9(7) + 11 + s = 180
105 - 31 + 63 + 11 + s = 180
153 + s = 180
s = 27
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