That is close but the answer is 75, please see post #9.
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Ganesh is right. You forgot the math tags on both ends of your latex.
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]]>y = f^{-1}\left(\frac{f(x_1)+f(x_2)+\cdots+f(x_n)}{n}\right),
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You get 3 equations in 4 unknowns:
Clear out fractions:
Subtract 1 from 2 and you get:
D = 68. Now use that in 2 and 3:
Subtract 2 from 1
A = 75.
]]>The average weight of three men A, B, and C is 84 kg. A fourth man D joins them and the average weight of the four becomes 80 kg. If E whose weight is 3 kg more than D replaces A, then the average weight of B, C, D, and E becomes 79 kg. Find the weight of A.
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