Please answer! what muscles do wide grip push ups work and are they good for boxing?

Pecs/ triceps: 'Wide' based push-ups work more pec major muscle group and some triceps. As you 'narrow' your push-up base the triceps muscle works more ... I would think any upper body workout such as push-ups would be helpful for strength for boxing . Best of Luck!

Don't forget legs : It's true, any good upper body workout will be helpful, but don't forget your legs. Remember, much of your punching power starts and builds from the legs and hips, allowing you to extend and throw with power at your distance. Punching ineffectively with just your arms will wear you out quickly during a round. So if boxing is the main concern, don't forget to work your legs and footwork.