Contribution #468

Problem: ru/11.1.7

Added 11.1.5 11.1.6 11.1.7 11.1.8 11.1.9

Editor: Aliaksandr Melnichenka ( @astrosander )

Time: November 7, 2023 at 09:45 AM

GitHub commit: 5d56818db6a8ed4897985a3382e8430a84cd645e

+243 -50 lines changed