Đáp án:
`N = (2021 + 7/135) - (1+ 2/135) - (3 + 5/135)`
`⇔ N = 2021 + 7/135 - 1 - 2/135 - 3 - 5/135`
`⇔ N = (2021 - 1 - 3) + (7/135 - 2/135- 5/135)`
`⇔ N = (2020 - 3) + ( (7 - 2 - 5)/135)`
`⇔ N = 2017 + 0/135`
`⇔ N = 2017 + 0`
`⇔ N = 2017`
Vậy `N = 2017`