Let's break down the problem step by step.

Step 1: Define Variables

• Let the cost price (CP) of each pen be $y$ Rs.
• Therefore, the total cost price for 20 pens is $20y = x$ Rs.

Step 2: Understand Selling Price at a Loss

• He sold each pen at the cost price of two pens, so the selling price (SP) of each pen is $2y$ Rs.
• The loss is 20%, so the loss per pen is $0.20 \times y$ Rs.
• Hence, the selling price with a 20% loss would be $y - 0.20y = 0.80y$ Rs.
• According to the problem, this selling price is Rs.36 less than $2y$.

Step 3: Formulate the Equation

• The equation based on the above information is: $0.80y = 2y - 36$
• Solving for $y$: $0.80y = 2y - 36$ $2y - 0.80y = 36$ $1.20y = 36$ $y = \frac{36}{1.20} = 30 \text{ Rs.}$

Step 4: Find the Total Selling Price at 30% Profit

• Now, if he sold each pen at a 30% profit, the selling price of each pen would be: [ \text{SP per pen} = y + 0