I have an MIP problem where $n$ different types of cars are delivering packages. Sometimes multiple types of cars are required to go to a single location. For example if car $1$ makes two deliveries to location $z$, car $2$ needs to make an equal amount of deliveries as well.
In other words: if an integer variable $x_n$ is larger than $0$ it should be equal to all $x_n$ for all $x_n$ larger than $0$
How do I capture this in constraints in linear programming?
I think I need to create a new decision variable $b_i$ that is $1$ if a car makes $1$ or more deliveries, and $0$ if there are no deliveries. From there on I need to somehow set the $x_n$ values equal. But how?