Which equation best models the data shown in the scatter plot?? pls help its due rn

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.

How do i take any fraction and make it into a decimal or percentage?

How do i simply this radical expression?