Use the distributibity of multiplication of rational numbers over their addition to simplify:
(i)`2/7xx(7/(16)-(21)/4)`
(ii) `3/4xx\ (8/9-40/1)`

Explanation

(i)`2/7xx(7/(16)-(21)/4)`
Taking `16` as LCM of `4` and `16`.
`=2/7xx(7xx1-21xx4)/16`
`=2/7xx(7-84)/16`
`=2/7xx(-77)/16`
`=1/1xx(-11)/8`
`=(-11)/8`

(ii) `3/4xx\ (8/9-40/1)`
Taking `9` as LCM of `9` and `1`.
`=3/4xx(8xx1-40xx9)/9`
`=3/4xx(8-360)/9`
`=3/4xx(-352)/9`
`=1/1xx(-88)/3`
`=(-88)/3`
Hence simplified.