there r 2 ways to do this...
(1) unit rate...
10/50 = 1/5 miles per minute
In 90 minutes......1/5 * 90 = 90/5 = 18 miles
(2) proportion..
10/50 = x/90.....10 miles to 50 min = x miles to 90 min
cross multiply
(50)(x) = (10)(90)
50x = 900
x = 900/50
x = 18 minutes.
