I have read that companyA now have 60% shares of companyB. Does it mean that companyA have the business decisions for CompanyB? or this still depends on the agreement or board seat?
One of the immediate side effects of gnasher729's answer is that -- at the very first shareholder meeting -- Company A will appoint "their people" to Company B's board of directors. It is they who will chose the CEO and President of Company B (or ensure that the existing CEO and President follow Company A's policies and goals).