The initial ratio - 6 girls:9 boys
This can be simplified to a 2:3 ratio (dividing by 3 on both sides of the ratio).
Then two more girls and three more boys join the team (new ratio - 8:12).
Simplify this ratio and you get 2:3 as well (division by 4).
So the ratio stays the same because the same ratio is present in both cases (2:3).
