Worked example 1
Evaluate 3x + 5 when x = 4.
Put the given value into the expression first. Substitute: 3(4) + 5. Multiply first: 12 + 5 = 17.
Answer: 17
Grade 6 Math · Topic 43
Evaluating Expressions
To evaluate an expression, plug a value in for each variable and simplify using the order of operations. Always wrap the substituted number in parentheses — this prevents sign and operation mistakes.
Lesson alignment: 6.EE.A.2 · Take your time. You can return to this lesson whenever you need it.
Explore visually
Evaluate an expression with tiles
Replace each x-tile with the given value, then count all the units.
Think first: If you replace each x-tile with the same number, what should you count next?
Ready? Reveal the model and try your prediction
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Follow the worked examples
Read each step, then cover the explanation and see if you can explain why it works.
Worked example 2
Evaluate 2a² - b when a = 3, b = 5.
Put the given value into the expression first. Substitute: 2(3)² - (5). Exponent: 2 · 9 - 5. Now multiply: 18 - 5 = 13.
Answer: 13
Try a few on your own
Work these on paper first. Open “Check” when you are ready to compare your answer.
- 4x + 3, x = 2
Check
11
- 5x - 7, x = 4
Check
13
- (x)/2 + 6, x = 10
Check
11
- x² + 1, x = 5
Check
26
- 3a + 2b, a = 4, b = 1
Check
14
- 2(x + 3), x = 7
Check
20
- x² - 2x, x = 4
Check
8
- a² + b², a = 3, b = 4
Check
25
Try this situation 1
The cost of n tickets is C = 12n + 3. How much do 5 tickets cost?
Show a worked solution
Answer: $63.
Start by writing the calculation clearly: C = 12(5) + 3 = 60 + 3 = 63.
Try this situation 2
The area of a rectangle is A = ℓ w. Find the area when ℓ = 7 ft and w = 4 ft.
Show a worked solution
Answer: 28 sq ft.
Use the area formula and substitute the given numbers: A = (7)(4) = 28.
Fresh questions · saved on this device
Practice this skill
Try a fresh set each time. Answer one question, check your thinking, and read the explanation. If you miss one, return to the visual model and try another round.
Question 1 of 50 correct so far
Session complete
Check what you learned
Answer these five questions on your own. You can review the explanations after you submit and try again whenever you like. This short check is for practice, not a grade.
Practice and finish
Try the linked topic quiz for more practice. If something is tricky, return to the example and look for the step that changes the numbers or representation.
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More Grade 6 resources
Use these free materials if you want another explanation, extra paper practice, or a broader review.