1. **Stating the problem:** We need to complete the expression and simplify algebraic expressions as given in the first problem a) from the user's message. 2. **Problem a) from 3 Dopolni:** Given: $$a + b + 5 = a + (\square + \square)$$ We want to find the two terms inside the parentheses that make the equation true. 3. **Explanation:** Since the left side is $$a + b + 5$$ and the right side is $$a + (\square + \square)$$, the terms inside the parentheses must be $$b$$ and $$5$$ to keep equality. 4. **Answer for a):** $$a + b + 5 = a + (b + 5)$$ 5. **Now, let's solve the first expression from 4 Izračunaj a):** Given: $$3a + (-5b + a)$$ 6. **Use the distributive property and combine like terms:** $$3a + (-5b + a) = 3a - 5b + a$$ 7. **Combine like terms $$3a$$ and $$a$$:** $$3a + a = 4a$$ 8. **Final simplified expression:** $$4a - 5b$$ **Summary:** - Completed the parentheses in problem 3 a) as $$b + 5$$. - Simplified the expression in problem 4 a) to $$4a - 5b$$.