The difference between successive discounts of $40\%$ followed by $30\%$ and $45\%$ followed by $20\%$ on the marked price of an article is $Rs. 12$. The marked price of the article is (in $Rs.$)

If the cost price of $12$ pens is equal to the selling price of $8$ pens,find the gain percent.

If the cost price of $21$ watches is equal to the selling price of $18$ watches,then what would be the gain percent in this transaction?

An article is listed at $Rs. 65$. $A$ customer bought this article for $Rs. 56.16$ and received two successive discounts,of which one is $10 \%$. Find the other discount in this discount scheme offered by the shopkeeper (in $\%$).

Rajesh purchased a mobile phone and a refrigerator for $Rs. 12000$ and $Rs. 10000$ respectively. She sold the refrigerator at a loss of $12\%$ and the mobile phone at a profit of $8\%$. What is her overall loss or profit?

An article is marked for sale at $Rs. 504$. The shopkeeper gives a discount of $5\%$ on the marked price and still earns a profit of $20\%$. What is the cost price of the article? (in $Rs.$)