Let's simplify the given expression step-by-step to find its equivalent form.

The expression is:
$5(3a + 5) + 6$

1. Distribute $5$ to both terms inside the parentheses: $5 \times 3a + 5 \times 5 = 15a + 25$

2. Add the remaining $6$: $15a + 25 + 6 = 15a + 31$

So, the simplified expression is:

$15a + 31$

None of the given options exactly match this simplified form. However, if you consider a minor typo or correction:

Option C (3a + 31) seems similar but has a coefficient mismatch for $a$.

If I were to guess the correct intended option, it should have been:

15a + 31 (which isn't listed exactly).

Do you want further details or have any questions?

5 Related Questions:

1. How do you distribute a number over addition inside parentheses?
2. What is the process to combine like terms in an expression?
3. How would you check if two expressions are equivalent?
4. How can we identify errors in mathematical options?
5. What are common mistakes in simplifying algebraic expressions?

Tip: Always double-check the distribution step in algebraic expressions to avoid errors in simplification.