$A=\frac{2020^{10}+2}{2020^{11}+2}$
⇒ $2020A=\frac{2020^{11}+2.2020}{2020^{11}+2}$
= $1+\frac{2.2020-2}{2020^{11}+2}$
$B=\frac{2020^{11}+2}{2020^{12}+2}$
⇒ $2020B=\frac{2020^{12}+2.2020}{2020^{12}+2}$
= $1+\frac{2.2020-2}{2020^{12}+2}$
Vì $2020^{12}+2>2020^{11}+2$
⇒ $\frac{2.2020-2}{2020^{11}+2}<\frac{2.2020-2}{2020^{12}+2}$
⇒ $2020A<2020B$
⇒ $A<B$