### 24 Answers

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- Jim MoorLv 76 months ago
Add

3 +6 = 9, so 7+6 = 13

Multiply

3*3 = 9 so 7*3 = 21

Exp:

3² =9, so 7² =49

Or an infinite number of equations...

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- 6 months ago
13, 21 or 49. I'm not sure what other relationships exist between the given numbers.

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- Anonymous6 months ago
Is related to 21.

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- daniel gLv 76 months ago
Probably 21, 'what' being a variable here is that, a variable.

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- electron1Lv 76 months ago
To solve this type of problem, use a proportion.

3 ÷ 9 = 7 ÷ x

3 * x = 63

x = 21

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- Jeff AaronLv 76 months ago
Arithmetically, 13

Geometrically, 21

Exponentially, 49

etc.

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- MarkLv 76 months ago
21 (3 x 3 = 9 and 7 x 23 = 21).

- darkhorse6 months agoReport
7 x 23 = 161 not 21.

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- oikoσLv 76 months ago
Unanswerable. It could be 21 (3x3=9, 3x7=21) or it could be 49 (3^2=9, 7^2=49). Or you could come up with complicated formulas for other numbers.

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