Please provide an explanation on how to do this.

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?

Consider the set of all four-digit positive integers less than 2000 whose digits have a sum of 24. what is the median of this set of integers?

Adesigner charges a one time fee of $200 plus $40 an hour for each project. write an expression to represent how much money the designer will make for a project