we know there are about 3.8 liters in 1 gallon. if Chris bought 10.4 gallons, that’s 10.4 * 3.8 liters
10.4 * 3.8 = 39.52 liters
as a proportion, we can write it as
3.8/1 = x/10.4
(number of liters per number of gallons. there are 3.8 liters per gallon, but we don’t know how many liters in 10.4 gallons yet, thus the x)
then you cross multiply (multiply one sides denominator to with the other sides numerator twice and set them equal)to get
1x = 3.8*10.4
simplify
x = 39.52 liters
hope this helped!