Answer:
The number of Douglas fir trees = 350
The number of Ponderosa pine trees = 500
Step-by-step explanation:
Let the number of Douglas fir trees = x
Let the number of Ponderosa pine trees = y
There are 850 Douglas fir and Ponderosa pine trees.
x + y = 850
y = 850 - x ⇒(1)
The company paid an average of $300 for each Douglas fir and $225 for each Ponderosa pine, and the company paid $217,500 for the trees.
300 x + 225 y = 217,500 ⇒(2)
substitute from (1) at (2)
300x + 225 (850 - x) = 217,500
Solve for x
300x + 225 * 850 - 225x = 217,500
300x - 225x = 217,500 - 225*850
75x = 26,250
x = 26,250/75 = 350
y = 850 - 350 = 500
So,
The number of Douglas fir trees = 350
The number of Ponderosa pine trees = 500