Given the molecular of the hexacoordinated complexes is `:`
`(1)CoCl_(3).6NH_(3)" "(2)CoCl_(3).5NH_(3)" "(3)CoCl_(3).4NH_(3)`
If the number of co-ordinated `NH_(3)` molecules in `(1),(2)` and `(3)` respectively are `(6),(5)` and `(4)` , the primary valency in `(1),(2)` and `(3)` are `:`

Explanation

To solve the problem, we need to determine the primary valency of the given hexacoordinated complexes based on their molecular formulas and the number of coordinated NH3 molecules.

### Step-by-Step Solution:

1. **Understanding Primary and Secondary Valency**:
- Primary valency refers to the ionizable valency, which corresponds to the oxidation state of the central metal ion. It is represented by the ions that can dissociate in solution.
- Secondary valency refers to the non-ionizable valency, which corresponds to the coordination number of the central metal ion. It is represented by the ligands directly attached to the metal.

2. **Analyzing the First Complex: CoCl3.6NH3**:
- The molecular formula indicates that there are 3 chloride ions (Cl⁻) and 6 ammonia (NH3) molecules coordinated to cobalt.
- Since Cl⁻ ions are ionizable, they represent the primary valency.
- Therefore, the primary valency for CoCl3.6NH3 is **3** (from the 3 Cl⁻ ions).

3. **Analyzing the Second Complex: CoCl3.5NH3**:
- Here, we have 3 chloride ions and 5 ammonia molecules coordinated to cobalt.
- Again, the Cl⁻ ions are ionizable and represent the primary valency.
- Thus, the primary valency for CoCl3.5NH3 is also **3**.

4. **Analyzing the Third Complex: CoCl3.4NH3**:
- In this case, there are still 3 chloride ions and 4 ammonia molecules coordinated to cobalt.
- The Cl⁻ ions remain the ionizable part, representing the primary valency.
- Therefore, the primary valency for CoCl3.4NH3 is also **3**.

5. **Final Summary**:
- The primary valencies for the complexes are:
- For CoCl3.6NH3: **3**
- For CoCl3.5NH3: **3**
- For CoCl3.4NH3: **3**

### Final Answer:
The primary valency in (1), (2), and (3) are **3, 3, and 3** respectively.