Answer
The $Cl$ atom has an oxidation number equal to $(+3)$, and each Fluorine atom has an oxidation number equal to $(-1)$.
Work Step by Step
According to the rule $6(a)$, a Fluorine atom has an oxidation number equal to (-1).
According to rule $3$, if "x" is the oxidation number for the chlorine atom:
$(x) * 1 + (-1) * 3 = 0$
x - 3 = 0
x = +3
The oxidation number for the chlorine atom in this compound is equal to $(+3)$.
