What is x when 30 divided by x equals 78?

To find the answer, just divide the dividend by the quotient: 30 ÷ 78 = 0.38461538461538

To prove this, let's compute 30 divided by 0.38461538461538: $\frac{30}{0.38461538461538} = 78$

How does it work?

Asking what the value of x could be when 30 divided by x gives a result of 78, is equivalent to solving the following equation:

$\frac{30}{x} = 78$

Multiply both sides by x: $\frac{30 x}{x} = 78 x$
$\frac{30 x}{x}$ is equivalent to $\frac{x}{x} \times 30$ , which simplifies to $1 \times 30$ (or just $30$ ).
Thus, the equation becomes: $30 = 78 x$
To find x, divide both sides by 78: $\frac{30}{78} = \frac{78 x}{78}$
Which gives, after simplification: $0.38461538461538 = x$ (or $x = 0.38461538461538$ )

So, if the dividend is 30 and the quotient is 78, the divisor is 0.38461538461538.