are 50-100 jumping jacks a night and 20-35 crunches a good way to lose weight?

Answer 1

for gaining maybe, not losing...
crunches build muscle, they dont burn any fat and will make your belly look bigger if you dont lower your body fat percentage.
the only fat burning exercise is cardio but you have to do it 4-6 times a week for average of 45min.
diet is a key to fat loss - make healthy food choices, eat 5-6 small meals a day, lots of fruit and veggies, protein, healthy fats and complex carbs, at least 8 glasses of water a day.

Answer 2

Not really, but hey.... anything is better than nothing.