Tính cách thuận tiện nhất : 80-81+82-83+84-85+86-87+88-88+90

$\color{#b3c3d4}{⸻⸻⸻⸸}\color{#9db0c2}{⛓Ƥเ}\color{#889eb0}{๓є}\color{#738c9e}{ђค⛧}\color{#5f7b8c}{⋆⸻⸻⸻}$

`80-81+82-83+84-85+86-87+88-88+90

`=80-81+82-83+84-85+86-87+(86+1+1+1+1)`

`=(80+1)-81+(82+1)-83+(84+1)-85+(86+1)-87+86`

`= 81-81+83+83+85-85+87-87+86`

`=86`