Cho 

- Hướng dẫn giải

$A=\frac{2018}{2019}+\frac{2019}{2020}>\frac{2018}{2020}+\frac{2019}{2020}=\frac{2018+2019}{2020}>\frac{2018+2019}{2019+2020}=B$

Vậy A > B