Can a sentence become an equation?
By the end of this lesson
Translate a short English sentence into an equation, solve it, and check in the story.
Remember
- Choose a letter and write what it stands for in a sentence.
- sum → + · difference → − · product → × · “is/gives/makes” → =.
- “2 more than x” is x + 2. “2 less than x” is x − 2. “twice x” is 2x.
- Solve with the methods you already have.
- Check in the story, not only in the algebra (“does 12 plus 8 really make 20?”).
Worked examples
Cover the answer. Try the steps on paper, then open them.
Example 1 — Plus is
“A number plus 8 is 20.”
- Let x be the number.
- x + 8 = 20
- x = 12
- Story check: 12 + 8 = 20 ✓
Answer: x = 12
Example 2 — Twice
“Twice a number is 18.”
- 2x = 18
- x = 9
- Twice 9 is 18 ✓
Answer: x = 9
Example 3 — Less than
“2 less than a number is 11.”
- x − 2 = 11 (start from the number, take 2 away)
- x = 13
- 13 − 2 = 11 ✓
Answer: x = 13
Check: Not 2 − x unless the sentence says “2 minus the number”.
Common mistakes
Slip “2 less than x” written as 2 − x.
Fix It is x − 2.
You start with x and remove 2.
Slip Skipping “let x be…”.
Fix If you do not name x, you will lose what the number means.
One short sentence.
Slip Checking only x = 12 and not “12 plus 8 is 20”.
Fix The story is the real-world check.
Both checks are good; the story one catches a wrong setup.
Try on paper first
Write the answer, then tap Reveal. These are not the quiz — they are warm-ups.
1. “A number minus 5 is 9.” Equation?
Answer: x − 5 = 9
2. Then x =
Answer: 14
3. “Three times a number is 24.” x =
Answer: 8
4. “A number plus 6 is 6.” x =
Answer: 0
Touch practice
9 tap / typeTap an option or type the answer. Retry any miss. Extra generated questions appear after the set if this topic allows it.
Optional picture lab
After practiceReal world
Word problems in exams and life.
Connect
Requirements become code.
⭐ Star quiz
9 questionsFinish the touch practice first if you can. Then answer without peeking. Read every “why”.