Help pleaseee! Greatly appreciated if you do

The sum of the reciprocal of a positive number and the reciprocal of 2 more than the number is 3/4 equation: the number is

Write as a product: ac^2–ad+c^3–cd–bc^2+bd

Ateacher wanted to buy a chair, a bookshelf, two tables and a desk. she spent $900 for all five items and the chair and the desk combined 70% of her total. if the bookshelf cost $50, how much did each of the tables cost?