Help help i mark brain just give me answers

45% of the trees in a park are apple trees. there are 27 apple trees in the park. how many trees are in the park in all?

Complete the solution of the equation. find the value of y when x equals to 6 4x+y=20

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.