← Chapter 42 Chapter 43: Substitution in Algebra Chapter 44 →

Chapter 43: Substitution in Algebra

✏️ Explanation

Substitution means replacing a letter with a number in an expression or formula.

🔍 Why It Matters

Essential for calculating formulas and evaluating expressions.

📌 Visual Flowchart

🧭 See chart: "Substitution Steps" (to be added)
1
Identify Variables
Find the letters in the expression
2
Replace with Values
Substitute letters with given numbers
3
Calculate
Work out the result step-by-step

✏️ Worked Example

If x = 4 and y = 2, evaluate 2x + y
Step 1: Substitute the values
2x + y = 2(4) + 2
Step 2: Calculate
= 8 + 2 = 10

🧮 Interactive Substitution Tool

Expression:
2x + y
Solution:
2(4) + 2
= 10

🔢 Practice Exercises

1. If x = 3, evaluate 5x
Answer =
2. If y = 2, calculate 3y + 1
Answer =
3. If x = 5 and y = 4, evaluate x + y
Answer =
4. If a = 2, evaluate a²
Answer =
5. If b = 10, what is b – 4?
Answer =

⚠️ Common Mistakes

  • Plugging in the wrong values
  • Ignoring operation order (e.g. brackets or powers)

✨ Quick Summary

Substitute, then calculate step-by-step.