X- (-8) = -15 help me

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

Sue's average score for three bowling games was 162. in the second game, sue scored 10 less than in the first game. in the third game, she scored 13 less than in the second game. what was her score in the first game?

Tom can paint the fence in 12 hours, but if he works together with a friend they can finish the job in 8 hours. how long would it take for his friend to paint this fence alone?