What are some exercise routines without using weights to get abs?

Now that I’ve lost so much weight I’m thinking more and more about actually looking good. I’d like to have more definition to my muscles in my arms, legs, and stomach, but I can’t afford to buy a fancy exercise machine or dumbbell set. What are some exercise routines without using weights to get abs? I looked online and saw that Usher does a thousand sit-ups every single day to get the abs he has, but who has time for that? Maybe if I was a rich singer I could get paid to exercise! Instead I’ve decided to do aerobics including sit-ups, push-ups, and a variety of other muscle-enhancing movements which will work on all the muscles in my body. There are many “ab workouts” online for free that you can find on a search engine, and I think I’ll try a new one each week for variety! I’ll have to post some photos when I get some super hot abs!

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1. What are some exercise routines to start out on for someone who does not exercise on a regular basis?
2. How do I lose stomach fat quickly with exercise routines that I can do at home?
3. How do weights work? How much amount of weights should a person lift?
4. How do I get in shape/exercise at home without exercise equipment?
5. How do you get stronger without weights or equipment?