Answer :

A = 1/2 bh 
where: A = area 
b = length of the base 
h = height of the triangle 

Using the given, 
33.6 = 1/2 (b)(4) substitute the given values 
33.6 = 2b simplify the right side; 1/2(4) = 2 
16.8 = b divide both side by 2 

Therefore, the length of the base is 16.8 inches.
Formula for the area of a triangle= 1/2(b*h)
area= 33.6
33.6*1/2= 16.8

So the length of the base is 16.8 inches