(12^3/5*8^3/5) ^5
I suspect that you mean (12^[3/5]*8^[3/5]) ^5
$$\\(12^{3/5}*8^{3/5}) ^5\\\\ 12^{(3/5)*5}*8^{(3/5)*5}}\\\\ 12^3*8^3}\\\\ 96^3\\\$$
You can finish it :)