There is no fixed or guaranteed way to make 17btc form 7btc.You can try different things like gambling or trading but in this way you can also loosed the 7 btc amount and if u dont want to risk then I dont think there is any way.
yes there is no fixed date or time but we can talk of posibilities , yes to me it is possible but not in short term invest you have to wait for such a long time if you really want to made 17 bitcoin from 7, other wise the other option is gambling, in gambling you can make 17 bitcoin from 7 very easily, but the risk is involve there and you can even lose your 7 bitcoin in gambling in no time.