Stock prices are adjusted on the Sunday of their first wide weekend to (opening weekend box office x 2.7), so in your example the stock would adjust to $121.50 ($45 x 2.7) This multiplier is variable for holiday weekends. All of that is explained in the Glossary, and also noted on the Calendar each week.
Once you've read the FAQs and Glossary feel free to come back with additional questions.
You really need to read through the Help topics at the bottom of this page - this will give you a basic understanding of the game. MojaveMegJun 08, 09:21