When solving subtraction problems, what should you do when there aren't enough counters to remove?

Can you simplify 4/7? 24 points will be awarded!

What is the square root of 45? (step by step working plz)

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