Tìm x: x-(1/6+1/12+1/20+1/30+1/42) * 14=2018

`x - ( 1/6 + 1/12 + 1/20 + 1/30 + 1/42 ) xx 14 = 2018`

`x - ( 1/ ( 2 xx 3 ) + 1/(   3 xx 4 ) + 1/ ( 4 xx 5 ) + 1/ ( 5 xx 6 ) + 1/ ( 6 xx 7 ) ) xx 14 = 2018`

`x - ( 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 + 1/6 - 1/7 ) xx 14 = 2018`

`x - ( 1/2 - 1/7 ) xx 14 = 2018`

`x - 5/14 xx 14 = 2018`

`x - 5 = 2018`

`x = 2018 + 5`

`x = 2023`

Vậy `: x = 2023`