You can choose to answer this with fractions or decimals. I'll choose fractions because we won't need calculators. 22 1/2 miles "in" 1/3 hour, means 22 1/2 mi divided by 1/3 hour.
22 1/2 = [(22×2) + 1] ÷ 2 = 45/2
So (45/2)mi ÷ (1/3)hr is the same as (45/2) × (3/1), or (45×3)/2 = 135/2, which is 67 1/2, or 67.5 mi/hr (mph).