Answer:
I think Leslie Is 20
Step-by-step explanation:
The length is 12, because if it's 9 inches wide it has two sides of 9 inches which is 18. Then subtract that from the intial value 42 to get 24. After, you divide 24 by 2 due to there being 2 sides of the box and 24 is the sum of both sides. Hopethis helps!
What is your level at school? I want to help you through the answers
I'm not sure how to write the rule, but every time you add one more to the sum of the last two. First, you add 1, then 2, then 3. 1+1=2 2+2=4 4+3=7 7+4=11 and so on. I hope this helps!