`8/9 - 1/72 - 1/56 - 1/42 - .... - 1/6 - 1/2`
`= 8/9 - ( 1/72 + 1/56 + 1/42 + ... + 1/6 + 1/2)`
`= 8/9 - ( 1/2 + 1/6 +... + 1/42 + 1/56 + 1/72_`
`= 8/9 - ( 1/( 1.2) + 1/( 2.3) + .... + 1/( 6.7) + 1/( 7.8) + 1/( 8.9))`
`= 8/9 - ( 1 - 1/2 + 1/2 - 1/3 + ... + 1/6 - 1/7 + 1/7 - 1/8 + 1/8 - 1/9)`
`= 8/9 - ( 1 - 1/9)`
`= 8/9 - 8/9`
`= 0`