One, it's impossible to "spot reduce." While you can target certain areas of your body in terms of building up the muscles in that area, you can't decide to just lose weight in your stomach, or your thighs, or your rear. It doesn't work that way. You can't remove subcutaneous body fat from specific areas of the body by doing exercises that target those areas. Doing hundreds of crunches will certainly strengthen your abs, but that won't reduce the amount of fat stored in your torso.
If you want to build muscle and burn fat at the same time, you have to perform circuit training three days per week. How can you achieve this? Indulge in full body exercises like lunges, push-ups, and pull-ups, for one set of 15 repetitions. Don't forget to follow every exercise with one minute of jumping rope. You should be able to burn around 500 to 600 calories per workout.