Help? please and thank you NO LINKS​

It takes a total of 6 hours to fill up an inground backyard pool using a standard house. a function can represent this situation to represent the amount of water in the pool until it is full a function of time the hose is running. determine the domain for the function

Express the following as a function of a single angle. cos(60) cos(-20) - sin(60) sin(-20)

With alll of except for the 2 that i did already