Let's analyze each pair of expressions step by step to determine which are equivalent:

A. $3 + 5a - 5$ and $3 + a$

Simplify the first expression: $3 + 5a - 5 = (3 - 5) + 5a = -2 + 5a$ The second expression is $3 + a$.

These are not equivalent because $-2 + 5a \neq 3 + a$.

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B. $2a + 15(5a)$ and $2a + 1$

Simplify the first expression: $15(5a) = 75a$ So, $2a + 15(5a) = 2a + 75a = 77a$.

The second expression is $2a + 1$.

These are not equivalent because $77a \neq 2a + 1$.

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C. $-18(-8a)$ and $-a$

Simplify the first expression: $-18(-8a) = 144a$ The second expression is $-a$.

These are not equivalent because $144a \neq -a$.

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D. $3a + 8a + (-8a)$ and $3a$

Simplify the first expression: $3a + 8a + (-8a) = 3a + (8a - 8a) = 3a + 0 = 3a$ The second expression is $3a$.

These are equivalent because $3a = 3a$.

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Conclusion:

The correct answer is D. $3a + 8a + (-8a)$ and $3a$.

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Do you want details or have any questions? Here are 5 related questions:

1. How do you simplify algebraic expressions with like terms?
2. What happens when you multiply negative numbers in algebra?
3. How can we factor an expression like $15(5a)$?
4. What are the properties of equivalent expressions?
5. How do parentheses affect operations in expressions?

Tip: Always combine like terms when simplifying expressions to see equivalency.