Multiply : (i)`3/4b y5/7` (ii) `3/7b y\ ((-4)/5)` (iii)`((-5)/9)\ b y\ 4` (iv) `((-36)/7)b y\ (-(28)/9)`

Explanation

Multiplying:
(i)`3/4` by `5/7`
Using cross multiplication:
`=3/4xx5/7`
`=15/28`
We get the answer as `15/28`.

(ii)`3/7` by `(-4)/5`
Using cross multiplication:
`=3/7xx(-4)/5`
`=-12/35`
We get the answer as `-12/35`.

(iii)`(-5)/9` by `4`
Using cross multiplication:
`=-5/9xx4`
`=-20/9`
We get the answer as `-20/9`.

(iv)`(-36)/7` by `(-28/9)`
Using cross multiplication:
`=-36/7xx(-28)/9`
`=16`
We get the answer as `16`.