Answer:
we have two boats moving in opposite directions! From the perspective of the starting point, it would look like the two boats started moving away from each other. However, imagine if you were standing on one of the moving boats. It would feel like you are standing still, and, relative to your position, the other boat would be moving away from you at your boat's speed of 10 mph plus the other boat's speed of 12 mph!
Since the two boats are moving in the exact opposite direction, their relative speed, or the speed they move relative to each other, is 10 mph + 12 mph, for a total of 22 mph. At that point, the equation is the same, Distance = Speed * Time.
33 miles = (10 mph + 12 mph) * T hours
33 miles = 22 mph * T hours
(33 miles) / (22 mph) = T hours
1.5 hours = T hours