Board Thread:General Discussion/@comment-32994909-20190221183650/@comment-35026689-20190221223033

That's off because the BG doesn't protect every target.

3/15 * 0/12 + 1/15 * 0/12 + 11/15 * 1/12 is what you need to do

There is an 11/15 chance of the BG having the potential to kill

But the GF has the potential to kill 12 targets

So if the BG is on a target which can be killed (11/15), there is only a   1/12 chance that the GF will hit that target