A frequency table records 20 pupils in total. It shows 7 pupils scoring 1 mark, 5 pupils scoring 2 marks and the rest scoring 3 marks. How many pupils scored 3 marks? Enter the number of pupils.

توضیح

The counts of pupils have to add up to the 20 recorded, so the missing count is 20 - 7 - 5 = 8. Answering 12 stops at the pupils already accounted for, and subtracting the scores 1 and 2 instead of the counts confuses the marks earned with the number of pupils who earned them.