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Word problemsArithmeticMiddle schoolabout 0:41

A number plus 7 is 15. What is the number?: animated lesson

A narrated, step-by-step word problems video lesson with captions. Final answer: The number is 8.

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Video with a synthetic English voice and captions. Pick another language for subtitles in that language, or open the interactive version.

Video narrated by a synthetic voice (Piper TTS, en_US-ljspeech-high voice (LJ Speech dataset, public domain)); the steps come from our maths engine and the answer was checked independently. Download MP4 (0.2 MB) · Captions (WebVTT)

Steps on screen

1. The problem
Worked example
A number plus 7 is 15. What is the number?
2. Step by step
1. Read the problem
2. Solve the linear equation
3. The answer
$\text{The number is 8}$
The number is 8
4. Check
- Substitute x = 8: (8) + 7 = 15 ✓

Transcript

The problem. Here is the problem: A number plus 7 is 15. What is the number? Let x be the number: “a number plus 7” becomes x plus 7.

Step by step. Read the problem. Let x be the unknown number. “a number plus 7 is 15” translates to x plus 7 equals 15. Solve the linear equation. 1x plus 7 equals 15 → x equals (15 minus 7) / 1 equals 8.

The answer. So the answer is The number is 8. Let x be the number: “a number plus 7” becomes x plus 7.

Check. Substitute x equals 8: (8) plus 7 equals 15, which checks out.

About word problems

Turn everyday situations about prices, speed, ages and interest into equations and solve them.

A number plus 7 is 15. What is the number?: Animated Lesson