A solution is .
Let
is strictly increasing, and is strictly decreasing, so the solution is unique.
this is not really simultaneous equation problem. you need more than one equation for that.
note that on the right, if you make x too big (bigger than 7), you get a negative answer. the left side is always positive, so you want to try x values that are less than 7. there is one positive solution (meaning you would try integer values for x). trial and error can find it