In a chess club, 2 girls and 7 boys are attending. To participate in a competition, a team of four people needs to be formed, which must include at least one girl. In how many ways can this be done?
The team includes either one girl or two. Let's consider both cases. If the team has two girls, then two boys can be added to them in $\mathrm{C}_{7}^{2}$ ways. If the team includes only one girl (who can be chosen in two ways), then the team can be supplemented with three boys in $\mathrm{C}_{7}^{3}$ different ways. Therefore, the total number of possible teams is $\mathrm{C}_{7}^{2}+2 \mathrm{C}_{7}^{3}=91$.

## Answer

91 ways.