What is x when 39 divided by x equals 78?

To find the answer, just divide the dividend by the quotient: 39 ÷ 78 = 0.5

To prove this, let's compute 39 divided by 0.5: $\frac{39}{0.5} = 78$

How does it work?

Asking what the value of x could be when 39 divided by x gives a result of 78, is equivalent to solving the following equation:

$\frac{39}{x} = 78$

Multiply both sides by x: $\frac{39 x}{x} = 78 x$
$\frac{39 x}{x}$ is equivalent to $\frac{x}{x} \times 39$ , which simplifies to $1 \times 39$ (or just $39$ ).
Thus, the equation becomes: $39 = 78 x$
To find x, divide both sides by 78: $\frac{39}{78} = \frac{78 x}{78}$
Which gives, after simplification: $0.5 = x$ (or $x = 0.5$ )

So, if the dividend is 39 and the quotient is 78, the divisor is 0.5.