Answer
We will need $7.5$ gallons of paint to cover $900$ square feet of wall.
Work Step by Step
On the $y-axis$, we have the area covered by the paint; on the $x-axis$, we have the amount of paint needed to cover a certain area.
Let's set up the equation to find the amount of paint, ($x$ value), needed to cover $900$ square feet ($y$ value):
$900 = 120x$
Divide both sides of the equation by $120$ to solve for $x$:
$x = 7.5$
This means that we will need $7.5$ gallons of paint to cover $900$ square feet of wall.
