Please help me with 8 and 10 I’m so confused!

Alawn mower manufacturer incurs a total of 34,816 in overhead costs and 388 per lawn mower in production costs. how many lawn mowers were manufactured if the average cost of productions is 660

∆red ≅ ∆ by rule will give brainiest if possible

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?