I never could remember how to solve these type of questions.

RAY: Tommy, Dougie and I are sitting around the office one day at Car Talk Plaza. We were noticing how dingy the place looked. We’d been there 15 years, and the place had never been painted. So, we decided to paint Car Talk Plaza.

We didn’t know which team of us was going to do it, so we sat down and decided to do a little math. We determined that Tommy and I together could paint the entire Car Talk plaza in 10 days. After all, we had a lot of painting experience as kids, having painted Dad’s car a couple of times with brushes.

Dougie and I could do it in 15 days. And, if Doug and Tom worked together, they could do it in 30 days.

The question is how long would it take each of us, painting by ourselves, to paint the whole of Car Talk Plaza?