Amap scale is 1 in.: 50 mi. two cities are 450 miles apart. how far apart are the cities on the map.

A ratio is the same thing as a fraction.
You should have 
If you want to make something in inches, but the miles are on the bottom, you will have to multiply the miles on top to get rid of it on the bottom,
Like this: 
That makes it 450/50, which is just 9 inches.

The answer is 9 inches.

I'll say power property,final answer