Mastering Expressions and Equations

📋 Course Outline

1. Evaluating expressions and solving equations

📖 1. Evaluating expressions and solving equations

📝 Essential Points

• When $a=3$ and $b=5$, $a+2b=3+2\cdot5=13$.
• Solving $3x+4=19$ gives $3x=15$, so $x=5$.

⚠️ Common Pitfalls & Confusions

1. For $a+2b$, students may compute $a+b$ instead of $a+2b$.
2. For $3x+4=19$, forgetting to subtract $4$ first leads to an incorrect $x$.
3. For $3x=15$, students may divide by the wrong number (not $3$) to get $x$.
4. Arithmetic errors can happen when evaluating $3+2\cdot5$ for $a+2b$.
5. Students may swap $x$’s value with the intermediate value $3x$.

✅ Exam Checklist

1. Substitute given values for variables to evaluate $a+2b$.
2. Compute $a+2b$ correctly when $a=3$ and $b=5$.
3. Solve a linear equation of the form $3x+4=19$ by isolating $x$.
4. Find $x$ correctly for $3x+4=19$.