Read the In Focus question carefully.
What is it asking?
How will you work out the answer?
What do we know?
What is the same about Ruby's and Sam's cranes?
What is different?
How many cranes did Ruby make?
What operation do we need to perform?
How do we know?
How many paper chains do they make altogether?
How can we use this number to find out how many cranes are in each paper chain?