I'm more of a visual person when it comes to puzzles like these so here's my take: 1 2 3 4 5 6 7 8 9 10 Mary B B A B A B B A B B 7 Dan B A A A

I'm more of a visual person when it comes to puzzles like these so here's my take: 1 2 3 4 5 6 7 8 9 10 Mary B B A B A B B A B B 7 Dan B A A A B A B A A A 5 Lisa B A A A B B B A B A 3 Colin B B A A A B B A A A ? First I remove the answers that everyone agreed on. We know that one of these 4 answers is wrong because of Lisa. 1 2 3 4 5 6 7 8 9 10 Mary _ B _ B A B _ _ B B 7 Dan _ A _ A B A _ _ A A 5 Lisa _ A _ A B B _ _ B A 3 Colin _ B _ A A B _ _ A A ? Next we can assume anything matching Lisa's remaining answers are wrong, so I will put an x for those. These we 100% know are wrong answers. 1 2 3 4 5 6 7 8 9 10 Mary _ B _ B A x _ _ x B 7 Dan _ x _ x x A _ _ A x 5 Lisa _ x _ x x x _ _ x x 3 Colin _ B _ x A x _ _ A x ? If you count both the remaining answers and the blanks, you'll see they equal to their score + 1. That 1 being that unknown of the 4 original blank columns where everyone agreed. So the answer for Colin would by 6 because he has 7 remaining answers.