Respuesta :

24 m  is the correct answer for your question
       
Area = (1/2)bh   
h = b-4

(1/2)b(b-4) = 48
b(b-4) = 48 : (1/2)
b² - 4b = 96
b² - 4b - 96 = 0
D = (-4)² - 4·(-96) = 16 + 384 = 400 = 20²
b₁ = (4-20)/2 = -8     ∅
b₂ = (4+20)/2 = 12

The length of the base = 12 m