To determine the probability that a child has a pet or a sibling using the Venn diagram, you would typically add the probabilities in each circle and then account for the intersection, ensuring not to double-count the overlapping section.
In mathematical terms, the probability can be expressed as:
\[ P(\text{Pet or Sibling}) = P(\text{Pet}) + P(\text{Sibling}) - P(\text{Pet and Sibling}) \]
You would need the specific values from the Venn diagram to perform the calculations. Enter the decimal value you find from your observations of the Venn diagram in the space provided.
If you have the specific numbers from the diagram, I can help you calculate it step-by-step!