For the power loss, because there are two transmission lines I was wondering why we didn't need to multiply the power loss by two?

I assumed you mean question 16, where you need to calculate the power loss.

The fact that there are two transmission lines DOES have an effect on the power loss, but you don't multiply it by two. You still use the formula:

Power Loss = (Current ^ 2)(Resistance),

but the resistance is the resistance of both the lines, hence:

Power Loss = [(P/V)^2] x (Resistance of one line x 2)

= [(4/2)^2] x (2x2)

= 4 x 4 = 16W

I hope this helps.