<human>:  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?
<bot>: How long is the second video? ** 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.
How long are the first two videos combined? ** The first two videos combined therefore for a 4+8=<<4+8=12>>12 minute run time.
How long is the third video? ** 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.
How many minutes does Brian spend watching animal videos? ** The total length of time spent is therefore 24+12= <<24+12=36>>36 minutes
#### 36