My guess is this is your first program, so I'll help out as much as I can.
Here are some problems you may be facing:
1) Have you imported FileOutputStream and PrintStream?
import java.io.FileOutputStream;
import java.io.PrintStream;
2) You attempted to create a TRY block, but you failed to take account of an error occuring. After the block, you need to include either a CATCH or FINALLY block. I will include an example of a CATCH block since that is the simplest and most useful for your situation.
CATCH Block: "catch(Exception e){System.out.println(e);}"
3) You did not initialize the variable "x". Give it a value before you attempt to use it in the formula.
4) You incorrectly attempted to use Math.POW(double d1,double d2).
Your wrote: "((b)*Math.pow((x*8)),-0.5)"
While it should be: "((b)*Math.pow((x*8),-0.5))"
Always make sure your brackets are in the correctly place. I also believe you have forgotten a plus ( + ) if the formula in your description is correct.
5) You incorrectly attempted to print out your results.
Your wrote: "System.out.println("The value of y is " y;"
While it should be: "System.out.println("The value of y is "+y);"
Your wrote: "new PrintStream(fout).println (" The value of y is" y;"
While it should be: "new PrintStream(fout).println (" The value of y is "+y);
Keep in mind to include a bracket to close the println() method and keep in mind that to add a number to a string, you have to close the string, include a plus ( + ) and then include the number you want to add. It also doesnt hurt to include a space after "is" so there will be a space between "is" and the number during the output.
6) Lastly, you have forgotten an ending bracket ( } ). Put one at the end or where you are wanting to end a code block.