A small tree was planted at a height of 8 feet. The tree has been planted for 16 months, and is now 57.6 feet tall. Which equation could be used to find x, the average number of feet the tree grew each month?

A.

16x + 57.6 = 8

B.

57.6x + 8 = 16

C.

8x + 16 = 57.6

D.

16x + 8 = 57.6

First you have to know what x and y mean in the equation. They told you in the problem that x is the avg # of feet the tree grew each month. That means that the number multiplied by x is the number of months.

Y will be the total height. That number is 57.6. When y = 57.6, the number that should be multiplied by x is 16.

The tree starts at 8 ft tall, not 0 feet, so the y-intercept in this equation should be 8, because even when 0 months have passed, it will be 8 ft tall. So you know the equation will have the + 8 in it added to the slope times x part.

It should be d. 16x + 8 = 57.6