CanIoffseta2017$30kcapital gainAGAINSTa2015scheduleC $20kbusinesslossplusa2016scheduleCbusiness$30k loss?

Can I offset a 2017 $30k stock sale capital gain AGAINST a 2015 schedule C $20k business loss plus a 2016 schedule C business$30k loss? And if so in what form do I do it?