What is x when 21 divided by x equals 12?

To find the answer, just divide the dividend by the quotient: 21 ÷ 12 = 1.75

To prove this, let's compute 21 divided by 1.75: $\frac{21}{1.75} = 12$

How does it work?

Asking what the value of x could be when 21 divided by x gives a result of 12, is equivalent to solving the following equation:

$\frac{21}{x} = 12$

Multiply both sides by x: $\frac{21 x}{x} = 12 x$
$\frac{21 x}{x}$ is equivalent to $\frac{x}{x} \times 21$ , which simplifies to $1 \times 21$ (or just $21$ ).
Thus, the equation becomes: $21 = 12 x$
To find x, divide both sides by 12: $\frac{21}{12} = \frac{12 x}{12}$
Which gives, after simplification: $1.75 = x$ (or $x = 1.75$ )

So, if the dividend is 21 and the quotient is 12, the divisor is 1.75.