If you mean: (6^3) / (12^4)
This is [6 x 6 x 6] / [12 x 12x 12 x12]
cancel the 6's into the 12's to get: 1 / [2 x 2 x 2 x 12] = 1 / 96
Or, if you have to show all the exponential steps,
Since 6 = 2·3, 6^3 = (2·3)^3 = 2^3 · 3^3
Since 12 = 4·3 = 2²·3, 12^4 = (2²·3)^4 = (2²)^4 · 3^4 = 2^8 · 3^4
So: (6^3) / (12^4) = [ 2^3 · 3^3 ] / [ 2^8 · 3^4 ]
= 1 / [ 2^5 · 3 ]
= 1 / 96