Simplest way is to get an ice cube and freeze the chewy. Then you can scrape it off with a knife.

A little bit of white spirit would also work, especially if it's ground into the webbing.

I found the ice cube method rather messy when I tried it and ended up with a wet, chewing gum ridden car seat. Try a coolbox freezer pack instead. No mess.

I've used WD40 to soften gum and scrape it away carefully with finger nail. Use a cloth to apply it - don't spray WD40 everywhere! You might need to wipe a damp cloth over patch afterwards.