If you multiply both sides by x to get rid of the denominator, you need to take into account 2 cases, one where x > 0 (and the inequality will keep the same sign) and one where x < 0 (and the inequality will reverse its sign).
first one is (-inf.,-5/3) u (2/3,+inf.)
In the question it is asking how many natural numbers are there that satisfy this equation? By this solution it seems to be infinite.