Can someone please help me? I don’t understand algebra

What is the value of x? enter your answer in the box. photo attached.

The graph below represents the number of dolphins in a dolphin sanctuary. select all the key features of this function.

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?