$18$ articles were sold at an average price of $\text{Rs. }15$. The cost price of $12$ articles was $\text{Rs. }16$ each. Find the cost price of each of the remaining $6$ articles if there was no profit/loss in the transaction.

1. Calculate the total Selling Price ($\text{SP}$) of all $18$ articles:
$$\text{Total SP}=18\times 15=\text{Rs. }270$$

2. Since there is no profit or loss in the entire transaction, the Total Cost Price ($\text{CP}$) must equal the Total Selling Price:

$$\text{Total CP}=\text{Total SP}=\text{Rs. }270$$

3. Calculate the total $\text{CP}$ of the first $12$ articles:

$$\text{CP of 12 articles}=12\times 16=\text{Rs. }192$$

4. Find the total $\text{CP}$ of the remaining $6$ articles:

$$\text{CP of remaining 6 articles}=270-192=\text{Rs. }78$$

5. Calculate the cost price of each of the remaining $6$ articles:

$$\text{CP per remaining article}=\frac{78}{6}=\text{Rs. }13$$