Ethan took a quiz with 15 questions. if he answered 3/5 of the questions correctly, how many did he get wrong?

I love this question!  It requires careful reading!  There are multiple ways to get the right answer, so here are a couple!  The sentence tells us the fraction of the questions he got RIGHT!  To find this out you must multiply 3/5 by the total number of questions (3/5 x 15 = 9  correct questions).  You then can subtract the 9 questions from the 15 total to find out the number that were INCORRECT/WRONG.  15 - 9 = 6 incorrect questions.  Another strategy would be to find the fraction of questions Ethan missed, which is one minus the fraction he got RIGHT.  1 - 3/5 or 3/5 + ___ = 1 (5/5).  He missed 2/5 of the questions, so you can multiply 2/5 by the total to get (2/5 x 15 = 6) 6 incorrect answers.  Hope this helps!