Today I decided I wanted to start deleting some apps off my rMBP which has the latest 10.10.3 update. When I go into my Launchpad and click on the the apps and the blink, some have the little X next to them and I can remove them. Others like Firefox for example does not. I am logged in as admin but I cannot figure out how to remove some of these apps from my computer. Anyone have any advice?