So you know that 30 + 30 + w + w = P. We also know the area is 240 square feet. Divide 240 by 30 to find the width of the area. 240 / 30 = 8. w = 8. So add 30 + 30 + 8 + 8 to find that P = 76. HOWEVER, remember that George is using part of his house as a wall instead of a fence. So subtract 8 from 76 to get 68 ft. George will need 68 ft. of fencing for his dog run.