You could well be right mafia but my answer is 27 months. Clue here is in the 3 and 9 your looking at thirds and ninths and returning to a straight line. It’s a simple 2d quiz which has a specific answer. The orbital image is just to get one focused in an entertaining way on a mathematical puzzle. You may be right in your conclusion but what if a meteor hits one of the satellites? what if one of the satellites breaks down? What if space junk hits one of the satellites? What if the sun dies? The questions just go on and on.
I cant see how this is correct – think about it , if one satellite ( the faster one ) takes 3 years to orbit the earth then using common sense it must take at least 3 years before it begins a second circuit in order to lap the slower moving one and line up with it again.