Put `StartSystem=>true` as an argument in the function mixedVolume to tell the method to use polyhedral homotopies. Polyhedral homotopies solve a system with the same Newton polytopes as the original system and with random complex coefficients. This random coefficient system can serve as a start system to solve the original input system.

- mixedVolume(..., StartSystem => ...) -- optional input for computation of mixed volume by solving a random coefficient system

The object StartSystem is a symbol.