If B=number of bees and F=number of flowers:
B=F+1 because there is one more bee than flowers.
If we take one flower away we get F-1. So there are 2(F-1) bees, and B=2(F-1).
That is, B=2F-2. But B=F+1, so F+1=2F-2, 3=2F-F=F. There are 3 flowers and B=F+1=3+1=4. There are 4 bees and 3 flowers.