What is x when 51 divided by x equals 78?

To find the answer, just divide the dividend by the quotient: 51 ÷ 78 = 0.65384615384615

To prove this, let's compute 51 divided by 0.65384615384615: $\frac{51}{0.65384615384615} = 78$

How does it work?

Asking what the value of x could be when 51 divided by x gives a result of 78, is equivalent to solving the following equation:

$\frac{51}{x} = 78$

Multiply both sides by x: $\frac{51 x}{x} = 78 x$
$\frac{51 x}{x}$ is equivalent to $\frac{x}{x} \times 51$ , which simplifies to $1 \times 51$ (or just $51$ ).
Thus, the equation becomes: $51 = 78 x$
To find x, divide both sides by 78: $\frac{51}{78} = \frac{78 x}{78}$
Which gives, after simplification: $0.65384615384615 = x$ (or $x = 0.65384615384615$ )

So, if the dividend is 51 and the quotient is 78, the divisor is 0.65384615384615.