Solution 3- using Process Builder

Another way to achieve the same business requirement is to use a process created on Process Builder. Here is the description of the next screenshot:

• A process on the Account object, which will fire when the out of business checkbox is checked
• Then the Update Records action will be fired, and it will update all the open Opportunity stages to the Closed-Lost stage related to an account which is marked as out of business

The following screenshot represents solutions for a similar business scenario using Process Builder:

Process Builder allows you to automate complex business processes using click not code.