lol here's an (another!) alternate way
Case 1: Each team has 1 person it in. So the first team has person A and the other team has person B. We need to choose 3 people in the first from 7. So 7C3. For the other team, we need to choose 3 people from 4. So 4C3. So total = 4C3*7C3*1C1 = 140. We...