Apply some gasoline on the cloth where the gum is stuck. Did you know, gasoline or petrol dissolves the gum? Use just little bit of gasoline since it is flammable and therefore hazardous.
Scrape off the excess gum on the cloth with a knife, putty knife or toothbrush.
Soak the cloth and then wash (as per the normal laundry instructions)
DON’T HAVE GASOLINE? Then use LIGHTER FLUID instead. It is a fluid which comes in a can used to fill cigarette lighters of old style.