Brianna part - i need how do you solve this

Ineed to know the answer to this algebra question.

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?

Xy x xy if a and b are positive integers such that a*b=9 and b*a=72 what is the value of a/b