85C - 170A = 306 ---------- (1)
255 + 85B = 714 ------------(2)
(1) + (2):
85C + 85A + 85B = 1020
Divide by 85 through:
A + B + C = 12
The total of A, B ad C is 12.
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Find average :
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The average of A, B and C is 12 ÷ 3 = 4
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Answer: The average of A, B and C is 4.
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