A letter stands for a number we do not know yet. "5 more than n" is n + 5. "3 times n" is 3n. Careful with "less than": 3 less than n is n − 3. "Twice n, plus 4" is 2n + 4.
Worked example
Which expression says twice b?
Answer:2b
The right answer is 2b. Turn the words into numbers one piece at a time: twice b is 2b.
For grown-ups: Whole-number exponents; expressions with variables; evaluate. Below: three problems to try with the worked answers, and a free printable sheet. Children can practise the same skill as a game, with no sign-up and no ads.
CCSS 6.EE.A.1–2
What this practises, for teachers
Practices whole-number exponents; expressions with variables; evaluate (6.EE.A.1–2). A printable sheet with its answer key, worked answers on the page, no accounts.
The right answer is 9x. Turn the words into numbers one piece at a time: 9 times x is 9x.
Which expression says y decreased by 5?
Show the answer and how
Answer:y − 5
The right answer is y − 5. Turn the words into numbers one piece at a time: y decreased by 5 is y − 5.
Which expression says 10 less than twice n?
Show the answer and how
Answer:2n − 10
The right answer is 2n − 10. Turn the words into numbers one piece at a time: 10 less than twice n is 2n − 10. "Less than" starts from the other number.