Brian loves watching animal videos online.  He watches a 4-minute video of cats.  He then watches a video twice as long as the cat video involving dogs.  He finishes up his video watching for the day by watching a video on gorillas that's twice as long as the previous two videos combined.  How many minutes does Brian spend watching animal videos?
Brian begins by watching a 4-minute video, and since the second video is twice as long that means the second video is 4*2= <<4*2=8>>8 minutes.
The first two videos combined therefore for a 4+8=<<4+8=12>>12 minute run time.
Since the third video is twice as long as the first two videos put together, that means it is 12*2=<<12*2=24>>24 minutes in length.
The total length of time spent is therefore 24+12= <<24+12=36>>36 minutes
#### 36