1. **Problem:** Simplify the expression $2a^2b + 3ab - a^2b + 2ab$. 2. **Step 1:** Group like terms. Terms with $a^2b$ are $2a^2b$ and $-a^2b$. Terms with $ab$ are $3ab$ and $2ab$. 3. **Step 2:** Combine like terms: $$2a^2b - a^2b = (\cancel{2} - \cancel{1})a^2b = 1a^2b = a^2b$$ $$3ab + 2ab = (3 + 2)ab = 5ab$$ 4. **Step 3:** Write the simplified expression: $$a^2b + 5ab$$ This is the simplified form of the given expression.