##K -> +1##
##O -> -2##
##Cl -> +5##
Wasn’t sure which element you were referring to but for a start ##K## and ##O## oxidation states are fixed by rules and .
##Cl## has variable oxidation states and can be determined algebraically :
If ##x## is oxidation number for ##Cl## and since no charge overall for the compound then
##(+1) + x + 3 xx (-2) = 0##
##x – 5 = 0 implies x=+5##