You can put this solution on YOUR website! 3^(7/2) = 3^(20x) ???
I can't make sense out of this. The problem mentions "rational exponents". So I have to guess that some kind of root is involved.
Please re-post your question making it clear what your expression is. If there is a root of some kind then either:
Use language like "square root of (x^2y)" or "cube root of {a^7b^5)" or "10th root of (ab^9)"; or,
since you seem to have learned something about using the three left and right braces on Algebar.com, use expressions like
sqrt(x^4v^8)
root(3, x^3u^11)
root(10, 123j^3k^30)
surrounded by three left and right braces.