Solving for the variable need all the steps written too

Rearrange the formula c^2 = a^2 + b^2 for b

Asap will give brainliest and a lot of points

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?