$\text{Bài 10:}$
`A=(3.20182018.20182020-5.20182017-2.20182018.20182018-5)/20182018`
`= (20182018.(3.20182020-2.20182018)-5.(20182017+1))/20182018`
`= (20182018.20182024-5.20182018)/20182018`
`= (20182018.(20182024-5))/20182018`
`= (20182018.20182019)/20182018=20182019`