For this case we have that the area of the shaded region is given by the subtraction of the large rectangle minus the small rectangle.
[tex]A_ {sr} = 30 * 16-10 * 8\\A_ {sr} = 480-80\\A_ {sr} = 400[/tex]
Thus, the area of the shaded region is [tex]400 \ ft ^ 2[/tex]
If the triangle must have the same area and a height of 25, then we have:
[tex]400 = \frac {1} {2} b * 25\\400 = 12.5b[/tex]
Dividing between 12.5 on both sides of the equation:
[tex]b = 32[/tex]
Thus, the base of the triangle is 32.
Answer:
32