Mrs. Rodriguez has 18 packages of pens in stock at her store on Monday.

On Tuesday, she has 5/6 the number of pens she had on Monday, which means...

On Wednesday, she has 2/5 of the number of pens she had on Tuesday, which means...
\\ Number \; of\; packages\; of \; Pens\; on\; Wednesday = \frac{2}{5} \; of \ 15=\frac{2}{5} \times 15=\frac{30}{5}=6
Conclusion:
Number of packages of pens does she have on Wednesday is 6 Packages