Answer:
Step-by-step explanation:
The image attached shows an example of this problem.
Givens
To find the margin, first we need to subtract
21.59 cm - 13.09 cm = 8.5 cm
Then, we divide this difference by two
8.5/2 = 4.25 cm
Therefore, Joelle should leave a margin of 4.25 cm at each side.