You will want this equation to be in y=mx+b, because you already have the slope and y-intercept. X will be the number of days she has had the plant, and Y will be the height of the tree, because it is the variable being affected by the X. The slope, or the M, is 2.5 because this is the number of centimeters the tree grows per day. The y-intercept is 5, because this is the height of the tree originally. So, the equation is Y=2.5X+5. To solve the number of days Margo will have had the plant, plug in 65 (the height of the plant after a certain amount of days) into the Y variable and solve for X. So, 65=2.5X+5. Subtract 5 from both sides to get 60=2.5X, then divide both sides by 2.5 to get X=24. So, she will have owned the plant for 24 days.
