1/3 + 1/6 + 1/10 + .... + 2/x.(x + 1) = 1.1999/2001; (11/1.12 + 1/12.23 + ....1/89.90) + x = 5/3

1/3 + 1/6 + 1/10 + .... + 2/x.(x + 1) = 1.1999/2001
(11/1.12 + 1/12.23 + ....1/89.90) + x = 5/3
(2/11.13 + 2/13.15 + ... + 2/19.21) - x - 4 + 221/231 = 4/3
1/3 + 1/6 + 1/10 + ... + 1/x.(x + 1):2 = 2001/2003
(1/1.2.3 + 1/2.3.4 + ... + 1/98.99.100).x = - 3
(x - 100)/24 + (x - 98)/26 + (x - 96)/28 = 3
(x + 1)/2 + (x + 1)/3 + (x + 1)/4 = (x + 1)/5 + (x + 1)/6
(x + 1)/2009 + (x + 2)/2008 + (x + 3)/2007 = (x + 10)/2000 + (x + 11)/1999 + (x + 10)/1998