`4/( 2 . 5 ) + 4/( 5 . 8 ) + 4/( 8 . 11 ) + ... + 4/( 65 . 68 )`
`= 4/3 . ( 3/( 2 . 5 ) + 3/( 5 . 8 ) + 3/( 8 . 11 ) + ... + 3/( 65 . 68 ) )`
`= 4/3 . ( 1/2 - 1/5 + 1/5 - 1/8 + 1/8 - 1/11 + ... + 1/65 - 1/68 )`
`= 4/3 . ( 1/2 - 1/68 )`
`= 4/3 . 33/68`
`= 11/17`