The rational number by which $\frac{-8}{39}$  should be multiplied to obtain $\frac{1}{26}$ is _______.

Given a rational number $\frac{-8}{39}$ .
Let the rational number = x.
According to the question,
$\frac{-8}{39}\times x=\frac{1}{26}$ 
$\Rightarrow x=\frac{1}{26}÷\frac{-8}{39}$ 
$\Rightarrow x=\frac{1}{26}\times \frac{39}{-8}$ 
Simplifying further,
$x=\frac{1}{2\times 13}\times \frac{3\times 13}{-2\times 2\times 2}$ 
$\Rightarrow x=\frac{1}{2}\times \frac{3}{-2\times 2\times 2}$ 
$x=-\frac{3}{16}$  

The required number is $-\frac{3}{16}$.