(-3a^{1/4})(9a)^{-3/2}
If you understood the properties, I suspect you would not be having difficulties with the problem. By the way, we have nothing to "solve" here, this is not an equation. Rather, we are "simplifying" the expression.
Now, use the properties and to finish it:
As a final step, you may want to convert to radical form, depending on the problem's instructions.