How do you use the missing pieces strategy to compare two fractions?

The difference between two numbers is one. three times the larger number minus two times the smaller number is 9. what are the two numbers

Acomputer store buys a computer system at a cost of $370.80. the selling price was first at $ 618, but then the store advertised a 20 % markdown on the system. answer parts a and b. a. find the current sale price.

Which number line correctly shows 0.8 + 0.3?