Answer i need and no one ever answers, must answers both or try to

I'm terrible at math any here is appreciated.

Asequence is defined recursively using the formula f(n + 1) =f(n) - 5. which sequence could be

Norder to get a certain shade of blue paint, a mixer must have 5 parts white paint to 3 parts blue. if 4 gallons of paint must be mixed, how many gallons of white paint must be used?