Answer: 33708
==========================================================
Step-by-step explanation:
There are currently 8,427 trees. Triple this value to get 3*8427 = 25,281
Add this result onto the previous number of trees to get 25,281+8,427 = 33,708
-----------
An alternative approach:
if we started off with x number of trees, and then added on three times as much, then we add on 3x more trees. This gets us x+3x = 4x trees total.
In this case, x = 8427, so that leads to 4*x = 4*8427 = 33,708