17. Summer nights in Cairo are much warmer than in London

=> In London, summer nights are not as warm as in Cairo.

18.  Fewer people die from flu than 50 years ago.

=> Not as …………many people die from flu as 50 years ago
19. There is less rain Tokyo than in Athens in January

⇒More rain is in Tokyo than in Athens in January.

20. There are fewer people in Taiwan than in Korea

=> The population of Korea is more than the population in Taiwan.