Answer:
28%
Step-by-step explanation:
Let number of children be 2x, then number of adults be 3x
Total number is 5x
Let number of children under 10 be 7y, number of children be 3y,
then total number of children is 10y
so 2x = 10y, x = 5y, y/x = 1/5
younger children = children under 10, number is 7y
so the % is 7y/5x = 7/5 * y/x = 7/5 * 1/5 = 7/25 = 28/100 = 28%