For question 3 you are told that the resistance varies linearly with length and inversly as the square root of the diameter. That means there is a constant (other things being equal) such that:

You are given the resistance, 30.9 Ohms of a 850 mm length of 0.122 mm diameter wire so:

when resistance is given in Ohms and length and diameter in mm.

Now you know you can use the first equation to find the resistence of any wire of the same material.

RonL