maths
posted by Jannie .
In a test there were 25 multiplechoice questions. They were marked as follows:
2 marks for each correct answer
0 marks for a nonattempt
1 mark for an incorrect answer.
Sarah attempted
4
5 of the questions and received 22 marks. How many questions did
she answer correctly?

Again we can set this up as two simultaneous equations
2 marks for each correct answer A
0 marks for a nonattempt (not interested in these)
1 mark for an incorrect answer B
A+B=20 (she only answered 4/5 of 25 questions)
2A+B=22 based on the marks
solve the two for A