Is this from a passage or text that you're given? If it is, then you can point out and explain statements that the author made in that passage which show that groups are more effective than isolated individuals.
Generally speaking, groups have more people so more perspectives and ideas so they have more creativity together. An individual who is isolated has limited ideas, even if they are creative. Also, working together in groups brings more confidence in an individual because they feel valued. And that leads to effectiveness.
