As a punishment for something naughty that we did, my little brother and I have to whitewash both sides of a fence. We start at the same time, and we each work at a constant rate.
If we each whitewash one side, I'll finish in 2 hours and my brother will finish in 3 hours. But I'm a nice kid, so after I finish my side, I go around to the other side and help my brother finish his side. From the time I start helping him, how many minutes does it take us to finish the job?
YOU paint 1 fence / 2hr = .5 f/hr
Bruh paints 1 fence/3 hr = .333 f/hr
when you are finished in 2 hours he still has 1/3 to go
1/3 fenc / ( .5 f/hr + .333 f/ hr) = 1/3 / .833 = .40 hr .40 * 60 min/hr = 24 minutes for you both to finish