When Vijay sells 12 pens, he gains the selling price of pens. Calculate his % profit?

By selling a pen for Rs 105 there is a loss of 30%. At what price (in Rs) the pen must be sold in order to gain 30%?

There is 10 % loss if a watch is sold for Rs 1440/-. At What price it is to be sold to get 15 % profit. 

Oranges are bought at 7 for Rs. 3. At what rate per hundred must they be sold to gain 33 % ? 

By a selling basket for Rs. 19.50, a shopkeeper gains 30 %. For how much should he sell it to gain 40 %? 

A merchant buys an article for Rs. 27 and sells it at a profit of 10 % of the selling price. The selling price of the article is: 

Sujatha sold 75% of her goods at a profit of 24% and the remaining at a loss of 40%. What is her gain/loss percentage on the whole transaction?

A wholesaler had 200 dozen of mangoes. He sold some of these mangoes at 20 % profit and the rest at 10 % profit, so that he made 13 % profit on selling all the mangoes. How many mangoes in dozens) did he sell at 20 % profit?