Introduction:
In electrolysis, the same quantity of electricity passes through two electrolytic cells containing a salt of metal X and zinc (Zn) respectively. The objective is to calculate the equivalent mass of metal X.

Key Concepts:
1. Faraday's Law of Electrolysis: It states that the amount of substance produced or consumed during electrolysis is directly proportional to the quantity of electricity passed through the electrolyte.
2. Equivalent Mass: It is the mass of a substance that reacts with or is produced by one mole of electrons.

Calculation:
To calculate the equivalent mass of metal X, we need to use the concept of Faraday's Law of Electrolysis.

Step 1: Determine the Faraday Constant (F)
The Faraday constant represents the charge of one mole of electrons and is given by:
F = 96,485 C/mol

Step 2: Determine the Charge (Q)
Since the same quantity of electricity passes through both cells, the charge (Q) will be the same for both cells.

Step 3: Determine the Moles of Zinc Deposited (n_zn)
Using Faraday's Law, we can calculate the moles of zinc (n_zn) deposited in the electrolytic cell containing zinc. The equation is given by:
n_zn = Q / (n * F)
where n is the number of electrons transferred in the balanced chemical equation.

Step 4: Determine the Moles of Metal X (n_x)
Since the same quantity of electricity passes through the cell containing metal X, the moles of metal X deposited will be the same as the moles of zinc deposited (n_zn).

Step 5: Determine the Equivalent Mass of Metal X
The equivalent mass of metal X can be calculated using the equation:
Equivalent mass = Mass of metal X / Moles of metal X
Since the moles of metal X deposited is n_x (obtained in step 4), we can rearrange the equation as:
Equivalent mass = Mass of metal X / n_x

Conclusion:
By following the above steps and using the given information, we can calculate the equivalent mass of metal X. The specific values and calculations will depend on the actual problem and its data.