How do we solve these type of questions

Combined megan and kelly worked 60 hours.kelly worked twice as many hours as megan.how many hours did they each worked?

For one history test, keith had to answer 40 questions. of these 40 questions, keith answered 28 of them correctly. what percent did keith get on his history test? round your answer to the nearest tenth if necessary

Consider the proof. given: segment ab is parallel to line de. prove: what is the missing statement in step 5?