Geometry, help please ???

The function models the number of accidents per 50 million miles driven as a function

State one method by which you can recognize a perfect square trinomial.

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?