The grass of a lawn grows slower the larger it gets. The length of the grass L is expressed in cm and the growth of the grass W in mm/day. If the grass is 2.7 cm tall at the end of day X, than it will be taller than 4cm 20 days later (assuming it will not be cut). this is a true or false statement, but i don't know how to show the work for it. This is what my teacher did,

2.7cm + 3 * 0.1cm = 3 cm + 17 * 0.06cm= 4.02cm > 4 cm. But i don't know why they used 3 and 17 days ( 3+ 17= 20) or or the 0.06cm

It has a graphic, you see it and you will know why. Good luck!