Hello, Myllhya. Whenever using unit rate, you set up a proportion: . Imagine the line in between x and y is the word 'per'. Finding how many feet in a given number of inches is the same as saying 'how many feet per inch', so this will be written as because feet becomes dependent on inches. Or, vice versa, the problem asks for inches for a certain amount of feet, you apply the same concept. The number of inches depends on feet, so you proportion is .
So you do 20%*426 to get 85.2 then you would subtract 85.2 from 426 because they sold 20% more than last year. On top of that the answer isn't 355 it is 340.8.
