What are the answers to this problem that makes cents from these this shouldn't really be easy for you guys

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

Asystem of equations has 1 solution.if 4x-y=5 is one of the equations , which could be the other equation ?

What is the value for this expression? 2e-5