Working together Daniel and Donnie can clean the llama pen i

Working together, Daniel and Donnie can clean the llama pen in 45 minutes. On his own, Daniel can clean the pen in an hour. How long does it take Donnie to clean the llama pen on his own?

Solution

(1/60 + 1/x) = 1/45

45(1/60 +1/x) = 1

45[(x + 60) / 60x] = 1

(45x + 2700) / 60x = 1

45x + 2700 = 60x

2700 = 15x

180 = x

180 minutes
Donnie can clean the llama pen in 180 minutes on his own.