Well this is a hard question to answer, but this is how i would put it.
You would take a number (lets use 15) and the second number (lets use 5) would determine how many times it would go into 15. In other words, 5 time x would equal 15 (5x=15). 5, being a factor of 15, would evenly fit into 15 three times.
If 1/10 of the tank is filled in 1/5 of an hour, then multiplying both of those by 5 you would get 5/10 of a tank being filled in a full hour, or answer choice A. Hope this helps! By the way, sorry for the incorrect answer a couple years ago :)
