What is x when 51 divided by x equals 42?

To find the answer, just divide the dividend by the quotient: 51 ÷ 42 = 1.2142857142857

To prove this, let's compute 51 divided by 1.2142857142857: $\frac{51}{1.2142857142857} = 42$

How does it work?

Asking what the value of x could be when 51 divided by x gives a result of 42, is equivalent to solving the following equation:

$\frac{51}{x} = 42$

Multiply both sides by x: $\frac{51 x}{x} = 42 x$
$\frac{51 x}{x}$ is equivalent to $\frac{x}{x} \times 51$ , which simplifies to $1 \times 51$ (or just $51$ ).
Thus, the equation becomes: $51 = 42 x$
To find x, divide both sides by 42: $\frac{51}{42} = \frac{42 x}{42}$
Which gives, after simplification: $1.2142857142857 = x$ (or $x = 1.2142857142857$ )

So, if the dividend is 51 and the quotient is 42, the divisor is 1.2142857142857.