The answer is 26. I'm assuming you don't need work.
Answer:
(a) 
(b) 
Step-by-step explanation:
Given
Variation: Inverse proportional.
This is represented as:

See attachment for table
Solving (a):
First convert variation to equation

From the table:

So, we have:





Substitute 4 for k in 


Solving (b): x when y = 25.
Substitute 25 for y in 

Cross Multiply

Divide through by 25

Take positive square roots of both sides


A1=8
common ratio=r
sum of 6 terms
S=a1+a2+a3+...+a6
=a1(1+r+r^2+...+r^5)
=a1(r^6-1)/(r-1)
but we're given S=74648
=>
8(r^6-1)/(r-1)=74648
Cross multiply and solve for r (by trial and error)
r^6-1=9331(r-1)
r=6
so
a(3)=a1*r^(3-1)
=8*(6^2)
=288
The answer I believe is 30