You cannot really find an exact value for the answer to this. Instead you can write the inequality in terms of the variables.
9x-7i >3(3x-7u)
9x-7i > 9x -21u
9x - 9x -7i > -21u
-7i > -21u
We need to divide both sides with -7 therefore we also need to flip the sign. Therefore, the answer is,
i<3u
