How many homes have both sprinkler systems and vinyl siding?

There are 80 homes in a subdivision. A realtor tells you that 50 of the homes have vinyl siding, 20 of the homes have automatic sprinkler systems, and 15 of the homes have both.

Modular Wall Panel Systems – Crucial in Affordable Panelized Homes Construction

Home manufacturers all over the world have recently started weighing different home building options  to ensure that the growing demand for affordable panelized homes are met with a considerable decrease in the home construction costs.
It required several years of research, engineering, testing, design & patent work to finally come out with efficient modular wall panel [...]