The ratio of selected girls to those who tried out is 12/30. The ratio of selected boys to those who tried out is 16/40. Simplify each ratio by dividing 12/30 by 6/6, and dividing 16/40 by 8/8; you get 2/5 for girls and 2/5 for boys. Therefore, the ratios are equivalent. For every 5 people that tried out, 2 were selected.