Need real as answers. Help

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?

An electrician cuts a 136 foot long piece of cable. one piece is 16 feet less than 3 times the length of the other piece. find the length of each piece