GENERAL

Question

Answer 1

$92$ to BCD is $1001 \ 0010$ which then is converted to graycode $1101 \ 1011$ which will choose $I_{219}$

Comments

$2^{n}-1$

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See input lines must be left side of MUX https://en.wikipedia.org/wiki/Multiplexer

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 input lines must be left side of MUX

in the question also, input lines are at left side of MUX right?

 if you are confusing, just calculate as normal MUX, at the end of the equation, you substitute the result of gray code as select lines

note that S₀ = LSB and S_n-1 = MSB of GRAY codes

Answer 2

Answer will be 11011011=219