First, the [[Mass|mass]] of a mixture and the total mass fraction, $m_{tot}$ and $c_i$.
$m_{tot}=\sum_{i=1}^km_i$
$c_i=\dfrac{m_i}{m_{tot}}\quad\text{and}\quad\sum_{i=1}^kc_i=1$
Secondly, we have the total number of [[Mole|moles]] in a mixture and the mole fraction, $n_{tot}$ and $y_i$.
$n_{tot}=\sum_{i=1}^kn_i$
$y_i=\dfrac{n_i}{n_{tot}}\quad\text{and}\quad\sum_{i=1}^ky_i=1$
Finally, a relation that should be familiar, the relation of [[Molar Mass|molar mass]], mass, and moles.
$n=\dfrac{m}{M}$