1. if sum is equal to 10 and total is less than 20, print the text string "incorrect.".
if( (sum == 10) && (total < 20) ) printf("incorrect.\n");
2. if flag is 1 or letter is not an 'X', then assign the value 0 to exit_flag, else set exit_flag to 1.
if( (flag == 1) || (letter != 'X') ) exit_flag = 0; else exit_flag = 1;
3. rewrite the following statements using a switch statement
if( letter == 'X' ) sum = 0; else if ( letter == 'Z' ) valid_flag = 1; else if( letter == 'A' ) sum = 1; else printf("Unknown letter -->%c\n", letter );
switch( letter ) { case 'X' : sum = 0; break; case 'Z' : valid_flag = 1; break; case 'A' : sum = 1; break; default : printf("Unknown letter -->%c\n", letter ); }