Respuesta :

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Answer:

[tex]\Large \boxed{\mathrm{When \ a \ number \ is \ not \ known}}[/tex]

Step-by-step explanation:

For example, a sum of a number and 6 is 12.

The number is unknown.

Let the number be x.

  • x + 6 = 12

We can solve for x (unknown number). Subtract 6 from both sides of the equation.

  • x = 6