Answer:
9 boards
Explanation:
2/3 of the porch= 6 boards
so to figure out how much one third of the porch needs you find half of what it takes to fill in 2/3 of the porch and you get 3.
so 3=1/3 of the porch
then you simply do 3times 3 or 3+3+3 and you get 9
so it takes 9 boards to fill the whole porch