Mathematics · Grades 6–9
Substitute into an expression
Substitute with brackets, then follow the order of operations.
The key idea
Substitute with brackets, then follow the order of operations.
ax + b → a × (value of x) + b
Worked examples
Evaluate 9x + 12 when x = -2.
9 × (-2) + 12 = -6
-6
Evaluate 2x + 26 when x = -1.
2 × (-1) + 26 = 24
24
Try it yourself
Evaluate 6x + 12 when x = 10.
Evaluate 6x + 18 when x = 8.
Check your understanding
Answers and marking notes
- 72
6 × (10) + 12 = 72
- 66
6 × (8) + 18 = 66
Further reading and review references
These are reference links, not copied exercises, institutional endorsement or proof of independent review.
Learning preview · teacher review required. Grade bands are approximate, not official curriculum alignment.