31 is not correct since 31 is not 4th power of any number.
(81÷16)^(3÷4) {(25÷9)^(3÷2) ÷ (5÷2)^-3 }
(81÷16)^(3÷4)=(3÷2)^3
=27÷8
(25÷9)^(3÷2)=(5÷3)^3
=125 ÷ 27
(5÷2)^-3 = (2÷5)^3
=8÷125
so what we needed is
(27÷8) × [(125÷27)÷(8÷125)]
=(27÷8)× (125÷27)×(125÷8)
=125 ×125 ÷(8×8)
= (5^3)^2 ÷ (2^3)^2
=((5÷2)^3)^2.
is the answer.
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