You can
put this solution on YOUR website!-10rs^9t^4
___________
2rs^2t^7
I am new to this format for entering aswers as well but you mentioned the whole expression is to the third power so
( -10rs^9t^4)^3
___________
(2rs^2t^7)^3
would be another way to write the problem.
The first thing to do is to simplify what is inside the parentheses
(-5s^7)^3
___________ Then -125s^21/t^9
(t^3)^3