Each of my daughters has as many brothers as sisters, but each of my sons has three times as many sisters as brothers. how many children do i have?

Put the number of daughters as x and number of sons as y.

For the first half of the statement:
Number of sisters any daughter has = x-1 ( because you can't be your own sibling)
Number of brothers = y

y=x-1.

For the second half:
Number of sisters any son has = x
Number of brothers any son has = y-1

3(y-1)=x

Solve as system of equations.
3y-3=x
3(x-1)-3=x
3x-3-3=x
2x=6
x=3
y=x-1=3-1=2

3 daughters and 2 sons.

Hope this helps!
Your fortune is "You can't have everything...where would you put them all?"

The answer is 9.7 cm