Grapefruit Salad with Fennel, Avocados, and Red Onion

There was a big sale in the grocery store's produce department this past weekend. Oranges, grapefruits, and mangoes were all ten for ten dollars, and avocados were four for five dollars. I stocked up, and then Maggy and I went back to the grocery store and we stocked up some more. We went through a