ALG009 · Algebraic expressions · Classes 6–9
Evaluating expressions
To evaluate an expression, replace each variable with its value and calculate, following the order of operations.
4x − 3Evaluating expressions
📐 Formula
substitute, then BODMAS
✏️ Worked example
4x − 3 at x = 2.5: 4 × 2.5 − 3 = 10 − 3 = 7.
🌍 Where it is used
Using formulas: area, speed, interest, temperature conversion.
❓ Quick check
Value of 2x + 7 when x = 3?
🏋️ Practice
EasyFind 5x when x = 6.
Answer: 30
MediumFind x² + 1 when x = −3.
Answer: 10
ChallengeFind 9C/5 + 32 when C = 25 (°F).
Answer: 77