a) `{8.25}/{2^5 . 15^3} = {2^3. 5^2}/{2^5.(3.5)^3}`
`= {2^3 . 5^2}/{2^5 . 3^3 . 5^3}`
`={2^3 . 5^2}/{2^5 . 5^3 . 3^3} = 1/{2^2 . 5 .3^3} `
`=1/{540}`
b) `{10^3 . 7^2}/{21^3 . 125} = {(2.5)^3 . 7^2}/{(3.7)^3 . 5^3}`
`={2^3 . 5^3 . 7^2}/{3^3 . 7^3 . 5^3}`
`= {2^3}/{3^3 . 7} = 8/189`