[user02@FC4 Lesson06]$ cat -n showmath.c

   1  #include <stdio.h>
   2
   3  int main(void)
   4  {
   5     printf("5 + 7 = %d\n", 5 + 7);
   6     printf("12 - 7 = %d\n", 12 - 7);
   7     printf("1.2345 * 2 = %f\n", 1.2345 * 2);
   8     printf("15 / 3 = %d\n", 15 / 3);
   9
  10     return 0;
  11  }

[user02@FC4 Lesson06]$ gcc -o showmath showmath.c
[user02@FC4 Lesson06]$ ./showmath
5 + 7 = 12
12 - 7 = 5
1.2345 * 2 = 2.469000
15 / 3 = 5