Question

I need this in the correct unit please.

Answer 1

We have that 1 inch is 50 miles. When the problem says to use a proportion, it is telling us to make that previous equation into a conversion factor.

There is 1 inch per 50 miles, or 50 miles per 1 inch.

We write a ratio 
$\dfrac{50 \ mi}{1 \ in}$.

We use our conversion factor and multiply across, cancelling units.

$(4.5 \ in)(\dfrac{50 \ mi}{1 \ in})=225 \ mi$