The given population models for the trees is given as:

It is required to find which forest will have a greater number of trees after 20 years and by how many.
To do this substitute t=20 in the equations of the models:


Hence, forest A has a greater number of trees after 20 years.
Calculate the difference:

It follows that forest A has a greater number of trees than forest B by 43 trees.
After 20 years, forest A has a greater number of trees than forest B by 43 trees.