The first picture is a picture of a ukelele. The ukelele's tuning pegs use gears to allow fine tuning of each string. The combination of gears include a normal gear and a worm gear for rapid gear down with minimal parts. This mechanism is also found in other string instruments, like the guitar. The second picture is a picture of a bicycle. The bicycle has many parts and mechanisms that make it a bicycle, but I would focus on the pedals. These bicycle pedals are used with special cycling shoes which have 'clicks' on them and the pedals have the mechanism that houses these 'clicks'. The main purpose of the cycling shoes is to prevent your feet from slipping from the pedals. It works with the help of a catch, which is attached to a spring. So when cycling, the shoes won't slip or come off unless you turn your foot sideways, releasing the catch. The third picture is of a watch. A watch uses lots of gears to transmit the energy to the hour, minute and second hand. It uses the concept of gearing down to 'slow down the motion of each hand, therefore in a way such that it synchronizes with the day and night, hour and minute.
This problem is something to do with the bicycle but not the bicycle itself. Due to little space available, it is pretty inconvenient to keep bicycles in the house. However, risking a stolen bicycle is not worth it. Therefore, a solution to this space problem is to use pulleys to haul the bicycle to the ceiling, and hang it there.