Answer:
8 ft
Step-by-step explanation:
The area (A) of a triangle = [tex]\frac{1}{2}[/tex] bh
where b is the base and h the perpendicular height
Using b = 20 and h = 12, then
A = 0.5 × 20 × 12 = 120 ft²
Using b = 30 and perpendicular height = h, then
0.5 × 30 × h = 120
15h = 120 ( divide both sides by 15
h = 8
