Answer:
p = 0.513
Step-by-step explanation:
There are 212 families with exactly 3 children. So in all, there are 212*3 = 636 children.
Of those,
The number of girls is:
81 + 76*2 + 31*3 = 326
That is, 326 girls out of 636 children.
Then
[tex]p = \frac{326}{636} = 0.513[/tex]