What is x when 51 divided by x equals 9?

To find the answer, just divide the dividend by the quotient: 51 ÷ 9 = 5.6666666666667

To prove this, let's compute 51 divided by 5.6666666666667: $\frac{51}{5.6666666666667} = 9$

How does it work?

Asking what the value of x could be when 51 divided by x gives a result of 9, is equivalent to solving the following equation:

$\frac{51}{x} = 9$

Multiply both sides by x: $\frac{51 x}{x} = 9 x$
$\frac{51 x}{x}$ is equivalent to $\frac{x}{x} \times 51$ , which simplifies to $1 \times 51$ (or just $51$ ).
Thus, the equation becomes: $51 = 9 x$
To find x, divide both sides by 9: $\frac{51}{9} = \frac{9 x}{9}$
Which gives, after simplification: $5.6666666666667 = x$ (or $x = 5.6666666666667$ )

So, if the dividend is 51 and the quotient is 9, the divisor is 5.6666666666667.