Dogwood cost = $15000
Red Maple cost = $30000
First, write an expression expressing what you know.
x = percent of inventory that's dogwood trees
(1-x) = percent of inventory that's red maple trees
So the expression looks like
0.26x + 0.17(1-x) = 0.20
Solve for x. Distribute the 0.17
0.26x + 0.17 - 0.17x = 0.20
Merge the x terms
0.09x + 0.17 = 0.20
Subtract 0.17 from both sides
0.09x = 0.20 - 0.17 = 0.03
Divide by 0.09 on both sides
x = 1/3
So one third of the inventory cost is dogwoods and two thirds is red maples. So
Dogwood cost = 45000 * 1/3 = $15000
Red Maple cost = 45000 * 2/3 = $30000