Susie's average score was 86 so if you take 86 x 4 it would equal 344 which is her total points scored on the four tests. Take the total 344 - 85 = 259; then 259 - 84 = 175; then 175 - 78 = 97. The 97 is Susie's fourth test score because when you combine the four individual test scores you get 344. Take 344 and divide it by 4 and you will 86 which was her average score. Fourth test is 97.
