There are 4 quarts in a gallon, and 2 pints in each quart. so take 10 gallons and multiply it by 4 then by 2 which gives you 80 pints in a gallon. or realize that there are 8 pints in a gallon so multiply 10 by 8 which again gives you 80.
80 pints in a gallon
there are 16 ounces in a pound, but you are trying to get back to the larger unit, rather than the smaller one, so you do the opposite of what we did in the first problem. We do the opposite of multiplying which is dividing. we divide 112 ounces by 16 to get back to pounds. 112 divided by 16 is 7
there are 7 pounds in 112 ounces
again, we're assuming that both triangles are similar, and thus using proportions.

we do not use the -10, because whatever value "x" may be, can't be negative or even 0.