Arif bought 17 pens of three colors-black , green and red. They cost Tk 10 and Tk 25 each respectively. The total amount that Arif paid was Tk. 205. If Arif bought twice as many green pens as red pens, how many black pens did he buy?

প্রশ্নঃ Arif bought 17 pens of three colors-black , green and red. They cost Tk 10 and Tk 25 each respectively. The total amount that Arif paid was Tk. 205. If Arif bought twice as many green pens as red pens, how many black pens did he buy?