You have ten pigeons. You want to give these pigeons away to some of your friends. The first friend picks a number of pigeons of
her choice for herself. After that you give away the remaining pigeons to the rest of your friends. If you give each of them 3 pigeons, 5 are left and if you give each of them 5 pigeons, 3 are left. How many pigeons did your first friend choose for herself?
