She drove a total of 39,333 – 38,948 = 385 miles
Assuming the tank was emptied on the 7th day, it took 11 gallons of gas to drive 385 miles.
She can drive at a rate of 385 miles per 11 gallons of gas.
\(\frac{385\,\text{miles}}{11\,\text{gallons}}\,=\,\frac{385\,\text{miles}\,\div11}{11\,\text{gallons}\,\div11}\,=\,\frac{35\,\text{miles}}{1\,\text{gallons}}\)
That is, 35 miles per gallon