well we know that his average score is 78 percent. so we need to use 78 with all the tests he took. so 78+78+78 is equal to 234. i tested each number. 234+86 is equal to 320. 320/4 (4 for the number of tests he took) is 80. so he needs a test score of at least 86 percent to raise his average score to 80% he could get a higher score but remember, he is trying to reach 80%
