The length of the minor axis is 4 
Step-by-step explanation:
Step 1 :
The given equation  is  [tex]\frac{(x-3)^{2}}{64}  + \frac{(y-7)^{2}}{4} = 1[/tex]
Here we see the denominator below the variable x is greater than below y. Hence the ellipse's major axis and the minor axis are parallel to x-axis  and  y-axis respectively
Step 2 :
The square of the semi minor axis will be the denominator of the y variable. So in the given ellipse ,
the square of the semi minor axis = 4
Hence the length of the semi minor axis  = [tex]\sqrt{4}[/tex]  = 2 
Step 3 :
The length of the minor axis = 2 times the length of the semi minor axis
                                                = 2 × 2 = 4
Answer : 
The length of the minor axis is 4