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( 3x )^3+( 2y )^3=( 3x+2y ) [( 3x )^2+( 2y )^2-xy ]. ⇒27x^3+8y^3=12( 9x^2+4y^2-6 )

and now, we have to find out the value of, 9x^2+4y^2

∴( 3x+2y )^2=( 3x )^2+( 2y )^2 +2( 3x )( 2y )

⇒( 12 )^2=9x^2+4y^2+12*6

⇒144=9x^2+4y^2+72

⇒144-72=9x^2+4y^2

⇒132=9x^2+4y^2

∴27x^3+8y^3=12(132-6)

⇒27x^3+8y^3=126.

hope that it will help.