All you have to do is add the number of vanilla and the number of chocolate, then divide the result by 24. You round up the result to the nearest whole number.
Like so: 377+935=1312 1312/24=54.67 55
So, she would have to refill it 55 times to use all the batter.
It would include the 8 hrs. of x miles per hour and the 7 hrs. of 325 miles per hour, giving the total miles. Then, as you eliminate, you can find out what (x) is.