Question:

Sally answered 100 questions in a test. She gets 1 mark for every correct answer. 2 marks are deducted for every wrong answer. She scored 79 marks. How many questions did she answer wrongly?

Method 1:

Method 2:

Correct answer –> 1 marks

Wrong answer –> deduct 2 marks ==> total penalty 3 marks (2+1)

100-79=21

21/3 = 7

She answered 7 questions wrongly.