Time should be on the x-axis and height should be on the y-axis. Remember to scale your graph evenly.
At what point does the plant have a height greater than zero?
The third week
Looking at your graph, try to see between which two weeks the line is the steepest.
This will be when the most growth occurred.
Determine how much total growth there was.
How much growth was in the last week?
Divide the 8th week growth by the total growth to find the answer.