Hi, I have been doing a lot of cardio and core exercises to get abs and loose fat. When school starts (august) I am going to start the heavy weightlifting again that I did during the year. I want to gain more muscle but I also want to keep the abs and the toning that I have from cardio (in the summer) I read I could work out 3x a week and in between do cardio (2 days) Is this OK or is there a better way?

This is a problem for a lot of people who want mass AND cut weight at the same time.

What you suggested will be fine... lifting weights and cardio in between. Just be sure to amend your diet so that it'll fit accordingly. Lots of protein, cut out junk, etc.

Good luck.