What is x when 87 divided by x equals 4?

To find the answer, just divide the dividend by the quotient: 87 ÷ 4 = 21.75

To prove this, let's compute 87 divided by 21.75: $\frac{87}{21.75} = 4$

How does it work?

Asking what the value of x could be when 87 divided by x gives a result of 4, is equivalent to solving the following equation:

$\frac{87}{x} = 4$

Multiply both sides by x: $\frac{87 x}{x} = 4 x$
$\frac{87 x}{x}$ is equivalent to $\frac{x}{x} \times 87$ , which simplifies to $1 \times 87$ (or just $87$ ).
Thus, the equation becomes: $87 = 4 x$
To find x, divide both sides by 4: $\frac{87}{4} = \frac{4 x}{4}$
Which gives, after simplification: $21.75 = x$ (or $x = 21.75$ )

So, if the dividend is 87 and the quotient is 4, the divisor is 21.75.