if we know 1 wrong answer and 4 correct and Lucy got 20 questions correct
5(4)= 20 correct answers
5(1)=5 incorrect answers
She misses 5 questions
we can do it in this way also
1 correct
2 correct
3 correct
4 correct
5 incorrect
6 correct
7 correct
8 correct
9 correct
10 incorrect
11 correct
12 correct
13 correct
14 correct
15 incorrect
16 correct
17 correct
18 correct
19 correct
20 incorrect
21 correct
22 correct
23 correct
24 correct
25 incorrect
we can count 20 correct and 5 miss questions
5 is the answer