c     Gauss Elimination Method
      parameter (n=3)
      implicit real*8 (a-h, o-z)
      dimension a(n,n),b(n),x(n)
       call input(a,b)
       call print(a,b)
       do 10 i=1,n
       an=a(i,i)
       do 20 j=i,n
        a(i,j)=a(i,j)/an
   20  continue
       b(i)=b(i)/an
       call print(a,b)
       do 30 k=i+1,n
        an=a(k,i)
        do 40 j=i,n
          a(k,j)=a(k,j)-an*a(i,j)
   40   continue
        b(k)=b(k)-an*b(i)
   30  continue
       call print(a,b)
   10 continue
      do 50 i=n,1,-1
       x(i)=b(i)
       do 60 j=i+1,n
        x(i)=x(i)-x(j)*a(i,j)
   60  continue
   50 continue
      do 70 i=1,n
      write(*,100) i,x(i)
   70 continue
  100 format (1x,'Ans.','x(',i1,')=',1pe12.5)
      stop
      end
      subroutine input(a,b)
      parameter (n=3)
      implicit real*8 (a-h, o-z)
      dimension a(n,n),b(n)
       a(1,1)=1.0
       a(1,2)=2.0
       a(1,3)=1.0
       a(2,1)=3.0
       a(2,2)=8.0
       a(2,3)=7.0
       a(3,1)=2.0
       a(3,2)=7.0
       a(3,3)=4.0
       b(1)=3.0
       b(2)=5.0
       b(3)=8.0
      return
      end
      subroutine print(a,b)
      parameter (n=3)
      implicit real*8 (a-h, o-z)
      dimension a(n,n),b(n)
        do 10 i=1,n
         write(*,*) (real(a(i,j)),j=1,n),real(b(i))
   10   continue
      write(*,*) '-----------------'
      return
      end