Let's use the variable x to represent the number of pounds of arbequina olives and y to represent the number of pounds of green olives.
The final blend will have 9 pounds, so we have:

And the final price is $20 per pound, so we have:
![\begin{gathered} x\cdot16+y\operatorname{\cdot}25=9\operatorname{\cdot}20\\ \\ 16x+25y=180 \end{gathered}]()
From the first equation, we have y = 9 - x. Using this value of y in the second equation, we have:

Therefore she needs 5 pounds of arbequina olives and 4 pounds of green olives.