Question

y varies inversely with twice the value of x.
When =8,x=2. Find y when =8

Answer 1

y=k*1/(2x)

Answer 2

use the same approach:
x=a*y
2=a*8
a=2/8=1/4
then if y=8
x=1/4 * 8
x=2

Answer 3

when y=8, then x=2?

find y when x=8?

i suppose this is what you mean to write

8=k*1/(2*2)
4*8=k
32=k

so we have
y=32*1/(2x)

y=16/(x)

y=16/8

y=2