Question 368255
{{{68 = (1/2)*h*(h+9)}}},
{{{136 = h^2 + 9h}}},
{{{0 = h^2 + 9h - 136}}}
(h+17)(h-8) = 0, or h = -17 or h = 8.  We eliminate the first value.  Thus the height is 8 feet.  The base is 8+9 = 17 feet. 

 Hope that matches the answer from the back of your book, hehehe...