# Unknown x

If we add to unknown number 21, then divide by 6 and then subtract 51, we get back an unknown number.

What is this unknown number?

Result

x =  -57

#### Solution:

$\dfrac{ x+21}{ 6} - 51 = x \ \\ \ \\ x = \dfrac{ 6 \cdot 51 - 21 }{ 1 - 6} = -57$

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