Question 910410
If you call the longest side (x) Then the second side is 1/2(x)  and the third side is x - 7. The sum of these three sides is 78 so this translates algebraically to:
x + 1/2 x + x - 7 = 78
2.5x = 85
x = 34 feet
so the longest side is 34 feet and the second side is 1/2 x = 17 feet and the third side is x - 7 = 27 feet so the triangle's three sides are
34,17, 27