Answer:
8 days.
Explanation:
Consider the question: Carlos has 4/5 of a tank of fuel in his car. He uses 1/10 of a tank per day. How many days will his fuel last?
To find the number of days Carlos' fuel last, we need to divide amount of fuel in tank by amount of fuel used per day as:

Convert into multiplication problem by flipping the second fraction as:



Therefore, Carlos's fuel will last for 8 days.