Effective tummy exercises?

I am trying to lose weight. I go to the gym, I normally do about a 1hr and a half - 2 hour workout. I can see a difference in my arms and legs, and I do floor exercises focusing on my tummy, but it's a stubborn area!

Yes I am dieting as well.

Any exercises you can recommend for me? I currently do 30-45mins of cardio and then my floor work I do 100 ab crunches and 100 ab twist crunches (you know the bicycle-y one) and 2 planks. I do other floor work but these are the ones focuses on my tummy.

Thanks in advance.
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Really struggling with BA, few of you have given fantastic answers, thank you x
Effective tummy exercises?
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