What mistake was made and what can i do in the future to avoid making the same mistake will mark brainlist

Kinu wants to buy topsoil for a section of her garden that has the dimensions shown in the figure. each bag covers 2 square yards. how many bags of topsoil should kinu buy? explain how you found the answer.

What are “like terms”? why can we only add like terms?

What is the slope of the equation y =