quick and easy dinner meals

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I just started dieting and exercising. I am a single mom (with full custody) of my 3 kids. So after I work all day long, I'm trying to go to the gym during the hours the gym still offers a playroom/daycare for my children. Does anyone have any suggestions of quick meals that could be prepared within 30 minutes or less? I'm open to any and all suggestions. Please keep in mind, I'm on a budget with grocery shopping.

Thank you all for your help