The K-team can paint a whole house in 60 minutes (super fast!!!). How much of a house can the team paint in 1 minute? The K-team can paint 1/60 of a house per minute.
The C-team can paint a whole hose in 80 minutes. How much of a house can the team paint in 1 minute? The C-team can paint 1/80 of a house per minute.
Suppose both teams paint for the same amount of time -- call the time t (minutes).
Combine the work they do to paint 1 whole house:

Multiply all the terms by the Least Common Denominator, LCD = 240.

Now, can you finish it? By the way, the answer is not a whole number! Hint: it will be between 30 and 40 minutes.