Answer:
23% probability the family has at least 3 children under the age of 21.
Explanation:
If a family is selected at random, what is the probability the family has at least 3 children under the age of 21?
15% have three children under the age of 21
5% have 4 children under the age of 21
3% have 5 or more children under the age of 21.
So:
15% + 5% + 3% = 23%
23% probability the family has at least 3 children under the age of 21.