`= (9/5)^5 xx (-20/27)^5`
`= 9/5 xx -20/27`
`= -4/3`
`b,, = 3^3 xx 3^(-2)`
`= 3`.
`(9/5)^5 : (27/-20)^5`
`= (9/5)^5 . (-20/27)^5`
`= [9/5 xx (-20/27)]^5`
`= (-4/3)^5`
`= -1024/243`
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`3^3 xx 9^(-1)`
\(=3^3.3^{2.\left(-1\right)}\)
\(=3^3.3^{-2}\)
\(=3^{3+\left(-2\right)}\)
\(=3^1=3\)