These problems are designed to help you practice becoming a fluent programmer. They are short and sweet, much like the types of questions you will be asked in a job interview.
You shouldn't be very concerned with getting the "right" answer as fast as possible. Rather, you should focus on improving with each problem. If it takes you a while to remember the syntax for writing a method or looping through a list, keep practicing and focusing on those skills. With enough practice, it will become second nature.
Each problem has driver code at the bottom so you can test your solution by running the code in Sublime (Command + B). If you're familiar with rspec, you should run the appropriate spec file for more accurate testing.