Multiply the rate per mile by the miles and the appropriate conversion factor.
[tex]\dfrac{1.2\,\text{oz}}{1\,\text{mi}}\cdot (15\,\text{mi})\times \dfrac{1\,\text{cup}}{8\,\text{oz}}=\dfrac{1.2\cdot 15}{8}\,\text{cup}=2.25\,\text{cup}[/tex]
The car leaked 2.25 cups of oil on the trip to grandma's house.