Olivia is taking a test that has 30 questions.She earns 9 points for every correct answer and loses 5 points for every wrong answer (questions left blank also count as wrong answers) . If Olivia’s score is 18 , how many questions did she answer correctly on the test .
1 answer
9 c - 5(30 - c) = 18 ... 14 c - 150 = 18