We are going to want to put this into slope-intercept formula. But first we need to find the slope
(5, 3) (25, 19)
(19-3)/(25-5)
16/20
4/5 = m
We then put this into the formula. But now we have to find b by plugging in one of the points as x and y.
y = 4/5x + b (10,7)
7 = 4/5(10) + b
7 = 8 + b
-1 = b
Our equation will be y = 4/5x -1.
Then we can plug in 40 as x to find the plant's height
y= 4/5(40) - 1
y= 32 - 1
y = 31 inches
Finally, the plant is 31 inches at 40 days.