Find out which part of the sentence has an error.
Kiran as well as Kamal are leaving for Mumbai.
Kiran as well as Kamal
With words like - 'with', 'together with', 'along with', 'as well as', the verb should follow the first subject. Since the first subject is singular in number (Kiran), so the verb should be 'is'.
Hence 'are leaving' is the correct option.