5/6= 1/2+ 1/3

7/ 12= 1/3+ 1/4

9/20= 1/4+ 1/5

So the original formula is equal to:

1/2+ 1/3- 1/3- 1/4+ 1/4+ 1/5- 1/5- 1/6+ 1/6+ 1/7- 1/7- 1/8+ / kloc-0//8+ 1/9- 1/9- 1/ 10= 1/2- 1/ 10=2/5