Hi everyone, I'm just stumped, I've tried but now I'm giving up.

An explanation of how to solve these would be much appreciated.A tank can be filled in 6 hours using two pipes. The larger pipe alone would fill it 5 hours sooner than the smaller pipe alone. How long would each pipe alone take?

A cyclist travelled at a certain speed to a town 30km away, then reduced speed by 4km/h and came back. If the cyclist had travelled at a steady 8km/h for the whole trip, the total time would have been half an hour less. What was the initial speed of the cyclist?