so 450 miles per hour
to see how many miles in 18 minutes you must see how many in a minute
an hour has 60 minutes
so divide 450 by 60 to see how many miles per minute
that is 15/2 miles per minute
now to see how many miles in 18 minutes
multiply 15/2 * 18
that is 135 miles in 18 minutes
Hope this helps :)