Statistics Help- Error of Margin and Estimated Standard Error

Hello,

This is the question from some of the practice problems in my online textbook. I already know what the answer is because it says when I got it wrong but it doesn't explain how they got the answer. To view a larger version of the image just click on it. Any help is appreciated.

Thanks

Does your textbook say what "SE" means? Do you have formula for calculating the "95%" and "90%" margin or error?