I am trying to deploy my first changeset from sandbox to production. I made few changes to visual force pages in my sandbox now I am trying to mock the deployment (to production) in Sandbox. when I validate it is giving my 100's of errors which are due to some packages that we use . Code does not have 75% coverage . How to handle this? Any help is appreciated

I am trying to deploy my first changeset from sandbox to production. I made few changes to visual force pages in my sandbox now I am trying to mock the deployment (to production) in Sandbox. when I validate it is giving my 100's of errors which are due to some packages that we use . Code does not have 75% coverage . How to handle this? Any help is appreciated