Harry drove for 6 hours on the freeway, then decreased his speed by 20 miles per hour and drove for 5 more hours on a country road. If his total trip was 648 miles, then what was his speed on the freeway?

His initial speed was 68mph. Using Distance = Rate * Time, we get:
Let r = speed for 6 hours,
r-20 = speed for 5 hours, so:
648 = 6r + 5*(r - 20).
Hope this wasn't in Wi because the max legal speed limit is 65mph!