Just fill in what you know and work it out:
You know the side of each square is k. So that means the AREA of each square will be k2. Since there are ten squares total, that means the ENTIRE area will be 10k2. So a=10k2.
Now get the perimeter: just count the number of sides that are bolded. There are 16 sides to the figure, and since each side equals k, that's 16k. So p=16k.
Since the question says p=a, that means 16k=10k2. Divide both sides by k to cancel it out, and you get 16=10k. Then divide by 10 on both sides and you get 16/10=k, which reduces down to 8/5=k.