Answer : y= 8/x
We know that linear function have constant slope.
In a linear function y=mx+b, the slope is m
Lets analyze each option
x + y = 100
y= -x +100
Here slope is -1. It is a linear function.
y=8/x
Here x is in the denominator and it is not in the form of y=mx+b
So it is non-linear function.
9 = 11x - y
y= 11x +9
Here slope is 11. It is a linear function.
x = y
y=x that has slope 1. It is a linear function.