50->34->20->19->15->7->4->2->73

So we can calculate like (50-2) + (73-2) = 71+48 = 119. what is reference for this trick and this is not working with other questions please someone confirm authenticity of this trick .

So we can calculate like (50-2) + (73-2) = 71+48 = 119. what is reference for this trick and this is not working with other questions please someone confirm authenticity of this trick .