Let's use the variable P to represent the number of people on the swim team before the 6 new people joined.
If after joining 6 more people, the number of people is 42, the sum of P and 6 is equal 42, so we have the equation:
![P+6=42](https://img.qammunity.org/2023/formulas/mathematics/college/2wsqkvqsjonpqm1r6aj1a4skmyghjdi8q1.png)
So the correct option is H.