6.EE.A.2a
6th Grade
Expressions & Equations
Writing Algebraic Expressions
Write expressions that record operations with numbers and with letters standing for numbers.
How to explain it
At this standard, students write algebraic expressions to represent word phrases.
The anchor students hold onto: Translate each phrase to its algebraic symbol. For subtraction, ORDER MATTERS — "less than" and "subtracted from" REVERSE the order of terms.
Sheet #18 Evaluating Expressions builds directly on this skill — students substitute values and compute the expressions written here. Subtraction-order patterns carry forward to equation work.
Worked examples
Example 1
3 more than twice n = ?
Step 1"twice n" → 2n; "3 more than" → +3
Step 2Write: 2n + 3
Step 32n + 3
Answer2n + 3
Example 2
10 less than a number n = ?
Step 1"less than n" → subtract FROM n
Step 210 subtracted from n → n − 10
Step 3n − 10
Answern − 10
Common mistakes
What students write
Student writes 3n for "the sum of n and 3" (confuses multiplication with addition).
The fix
3n means 3 × n. "The sum of n and 3" is n + 3.
Try this
A student writes 9 − n for "9 less than a number n." Identify the error and write the correct expression.
What students write
Student writes 8 − n for "8 less than n" (reverses subtraction order).
The fix
"Less than" reverses order: "8 less than n" = n − 8, not 8 − n.
Try this
A student writes 3n for "the sum of a number n and 3." Identify the error and write the correct expression.
Teacher tip
Head off the two predictable errors before they happen. First: 3n means 3 × n. "The sum of n and 3" is n + 3. Second: "Less than" reverses order: "8 less than n" = n − 8, not 8 − n.