What is x when 42 divided by x equals 15?

To find the answer, just divide the dividend by the quotient: 42 ÷ 15 = 2.8

To prove this, let's compute 42 divided by 2.8: $\frac{42}{2.8} = 15$

How does it work?

Asking what the value of x could be when 42 divided by x gives a result of 15, is equivalent to solving the following equation:

$\frac{42}{x} = 15$

Multiply both sides by x: $\frac{42 x}{x} = 15 x$
$\frac{42 x}{x}$ is equivalent to $\frac{x}{x} \times 42$ , which simplifies to $1 \times 42$ (or just $42$ ).
Thus, the equation becomes: $42 = 15 x$
To find x, divide both sides by 15: $\frac{42}{15} = \frac{15 x}{15}$
Which gives, after simplification: $2.8 = x$ (or $x = 2.8$ )

So, if the dividend is 42 and the quotient is 15, the divisor is 2.8.