Answer
$\frac{n_A}{n_B}=\frac{1}{x}$
Work Step by Step
We know that
$v_A=xv_B$....eq(1)
and $v_A=\frac{c}{n}$....eq(2)
similarly $v_B=\frac{c}{n_B}$....eq(3)
Substituting eq(2) and eq(3) in eq(1), we obtain:
$\frac{c}{n_A}=x\frac{c}{n_B}$
$\implies \frac{1}{n_A}=\frac{x}{n_B}$
$\implies \frac{n_A}{n_B}=\frac{1}{x}$
