6.EE.A.2c
6th Grade
Expressions & Equations
Evaluating Expressions
Evaluate expressions at specific values of their variables, including expressions that arise from real-world problems.
How to explain it
At this standard, students evaluate algebraic expressions by substituting given values.
The anchor students hold onto: SUBSTITUTE → then follow ORDER OF OPERATIONS. Multiply and divide BEFORE you add or subtract.
Sheet #19 Combining Like Terms simplifies expressions before evaluating — the substitution fluency here is essential for all future equation-solving work.
Worked examples
Example 1
Evaluate 4n + 7 when n = 3
Step 1Substitute n = 3: 4(3) + 7
Step 2Multiply first: 12 + 7
Step 319
Answer19
Example 2
Evaluate 2n² when n = 3
Step 1Substitute n = 3: 2(3²)
Step 2Exponent first: 2(9)
Step 318
Answer18
Common mistakes
What students write
Student adds before multiplying: evaluates 3n + 5 at n = 4 as 3(4 + 5) = 27.
The fix
Order of operations: multiply FIRST. 3(4) + 5 = 12 + 5 = 17.
Try this
A student evaluates 2m + 6 at m = 5 and gets 22. Identify the error and find the correct value.
What students write
Student applies the exponent to the coefficient: evaluates 2n² at n = 4 as (2×4)² = 64.
The fix
The exponent applies only to n. 2n² = 2(n²) = 2(4²) = 2(16) = 32.
Try this
A student claims n − 8 and 8 − n are equal when n = 10. Evaluate both and explain whether the student is correct.
Teacher tip
Head off the two predictable errors before they happen. First: Order of operations: multiply FIRST. 3(4) + 5 = 12 + 5 = 17. Second: The exponent applies only to n. 2n² = 2(n²) = 2(4²) = 2(16) = 32.