Final answer:
To apply the distributive property and factor out the greatest common factor of 15 + 21, we find that the GCF is 3, giving us 3(5 + 7) or 36 after simplification.
Step-by-step explanation:
The student's question involves applying the distributive property to factor out the greatest common factor. To do this, we need to identify the greatest common factor (GCF) of the numbers in the expression. In the expression 15 + 21, the GCF of 15 and 21 is 3 because it is the largest number that divides both 15 and 21 perfectly. Applying the distributive property, we factor out the GCF from both terms. As a result, the expression becomes:
3(5 + 7)
After factoring out the GCF, we can add the numbers within the parentheses, giving us a final answer:
3(12) or 36
This demonstrates how we can use the distributive property to simplify expressions by factoring out the greatest common factor and then evaluating the simplified expression.