The average test score was 90 and Marco scored 10% less so 90*.10 = <<90*.10=9>>9 points lower
The average test score was 90 and Marco scored 9 points less so his test score was 90-9 = <<90-9=81>>81
Margret received 5 more points than Marco whose test score was 81 so she made 5+81 = <<5+81=86>>86 on her test
#### 86