Symbolic solution to an exponential function

Hi All, I have a function which including two exponential components, whose power factor x and y are different. I was trying to solve it by hand or by Mathcad solver, but did not succeed. Would anyone give me the instruction how to do this?

Since an approximated solution is also acceptable, I  also tried to use the brute force method, in using match(0.9, XXX) and match(0.1, XXX) to solve, but it seems an exact match cannot be achieved. If someone can teach me how to get the approximated match, that would also be very helpful. Thank you!