I know exactly what you mean. I'm not good with math either. I work in retail as a sales associate for a large retail store. I'm also cashier-trained. Nowadays registers are automatic; meaning they tell you how musch to give as change, after typing in the money given. You will have to be cashier-trained, and be taught how to serve costumers in a quick past. You will also be trained what to do if a costumer pays by a credit or debit card; next they'll train you how to give cashback.
Then you'll be trained how to work with gift certificates. It's not a bad job, but costomer can get nasty and rude at the registers. Depending on the store; theres also in-stock positions, costomer service positions, salesfloor positions, overnight stocking/recieving positions, and more. You have to check and see with managment of the store; to see what jobs they are offering if any.
Make a resume and make sure you are clean, well dressed, calm, quiet, easy-going, and have a good personality when applying for a job. You can gain a lot of work experience regardless of where you are working at; any type of store, coffee shop, hotel, resturant, or at a office of sometype.
If you apply for a job; next you call the employer about your applicantion, and if they tell you they don't want you because you don't have experience; ask them "How can I gain job experience, If no one will hire me?" See what they say.
Getting a job isn't easy today.