Answer:
Douglas fir trees are 350 in number and Ponderosa pine trees are 500 in number.
Explanation:
Let the number of Douglas fir be denoted by 'x'
Let the number of Ponderosa pine trees be denoted by 'y'
The company paid average of $300 for each Douglas fir and $225 for each Ponderosa pine.
This gives,
for total Douglas fir trees and
for total Ponderosa pine trees.
Total amount paid by the company = 217500
Also given, there are 850 Douglas fir and Ponderosa pine trees which means ;
or
......................(1)
.............(2)
Putting the value of 'x' from equation 1 into equation 2.

Now, solving this equation we get,




And we know

So, x =

Hence, Douglas fir trees are 350 in number and Ponderosa pine trees are 500 in number.