Answer:
Juan scored 84 points on his first exam.
Step-by-step explanation:
---- ASSUMPTIONS: First Exam = X Midterm Exam = X + 5 Final Exam = X + 13 Mean Average Score for the 3 exams above = 90 ---- SOLUTION: 90 = [X + (X + 5) + (X + 13)] / 3 90 * 3 = [X + (X + 5) + (X + 13)] 270 = 3X + 18 270 - 18 = 3X 252 = 3X 252 / 3 = X 84 = X Conclusion: Juan scored 84 points on his first exam. (See below for proof) ---- PROOF: First Exam = X = 84 Midterm Exam = X + 5 = 89 Final Exam = X + 13 = 97 Mean Average of 90 points --> [84 + 89 + 97] / 3 = 270 / 3 = 90