1. **State the problem:** Simplify the expression $8a + (-3b + 5a)$. 2. **Apply the distributive property and combine like terms:** The expression inside the parentheses is $-3b + 5a$. We can rewrite the original expression as $8a + (-3b) + 5a$. 3. **Group like terms:** Group the terms with $a$ and the terms with $b$ separately: $(8a + 5a) + (-3b)$. 4. **Add the coefficients of like terms:** $8a + 5a = (8 + 5)a = 13a$. 5. **Write the simplified expression:** $13a - 3b$. 6. **Final answer:** $$13a - 3b$$