How many lemons batteries would it take to start a car?

How many lemons batteries would it take to start a car?

Note: All numbers must be entered as 5000 or 5e3 or 5.0e3 and not with commas as in "5,000" and not as fractions as in "3/4" and not as percentages as in "70%".

Please explain/break down these problems for me so that I can practice on other similar problems.