3^x×9^x×27^x

=3^x×3^(2x)×3^(3x)

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

=3^(6x)=3^ 12

So 6x= 12.

The solution is x=2.

Where 3 x represents the x power of 3.

Hope to adopt, if you don't understand, welcome to ask questions.