What is the value of the missing angles

Which property is illustrated by the following statement? if hxa rgi, then rgi hxa.

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

Solve 2x+y=3 x+y=5 in substitution method