happy_2[1]_% cat kadai7-2.c
#include <stdio.h>

main()
{
    double f, c;
    int i, n;
   
    f=0.0;
    while( f<=200 )
    {
         c = ( 5.0/9.0 ) * (f - 32.0);
         printf("%3.0f %6.1f\n",f,c);
         f = f + 20.0;
    }
}
happy_2[2]_% gcc -o kadai7-2 kadai7-2.c -lm
happy_2[3]_% kadai7-2
  0  -17.8
 20   -6.7
 40    4.4
 60   15.6
 80   26.7
100   37.8
120   48.9
140   60.0
160   71.1
180   82.2
200   93.3