Linear, because the graph of the line is just a straight line without any curves, and the power of x is 1. If x was raised to the second, third, fourth, etc. power, it would be a nonlinear equation.
The midpoint, if the endpoints are (x₁,y₁) and (x₂,y₂):


The midpoint of AB is (4,3).
Well, there isn’t really an end for numbers...
However; The biggest number referred to regularly is a googolplex (10googol), which works out as 1010^100. That isn’t the end to numbers but it is a huge one. We will replace that with ‘all the numbers in the world’.
106 is the exponent equivalent to 1 million
So your question would be:
106 x 1010^100 =
However I don’t believe there is a calculator that large.
The answer to the problem is
y=1/2x