In cooperation with Outdoor Research, the American Mountain Guides Association has made several videos for beginning level climbers.
In this video, AMGA Instructor Team Member and former AAI Guide Angela Hawse demonstrates how to equalize two slings off three pieces.
The technique that she uses in the video is often referred to as an "anchor in-series." The reason for this is because she has essentially just built an anchor on top of an anchor.
It's important to note that one piece in this configuration is receiving half the weight of the system, while the other two are only receiving a quarter each. This may not matter...but then again, it might...
--Jason D. Martin