Answer:
26cm
Explanation:
In a parallelogram both sets of sides are parallel to eachother meaning that the sides across from eachother would be the same length. So because one side is 8cm that means the side across from it is also 8 cm and same for the 5 cm sides. Therefore the side lenghts are 8,8,5 and 5 so we can add those together to get the perimeter 8+8+5+5=26
I hope this helps and please don't hesitate to ask if there is anything still unclear!