with a capital of 17 bitcoin? you want to get 7 bitcoin. it may even be more than that, but you have to have a commitment, my advice BTC that you use for the new coin trading, because of the new coin trading percentage we get to be 2-7x from the initial price. Do not ever be tempted kind of gambling! 
You did not get the point, he does not have a capital of 17 bitcoins from which he wants to get 7 bitcoins, but he has 7 bitcoins from which he wants to make 17 bitcoins which is not possible to be done in just one trade, though it can be done but not so soon, because not everytime you will get profits in trading so you will have to continue it for sometime and at the end the percentage of win and lose will tell you how much you have earned.