Of course, expressions can contain variables. With arithmetic expressions, the type of the variable determines what type of operations are performed.
What is displayed by this program:
#include <stdio.h> /* Puzzle E11 -- variables */ int main() { int a = 7; int d = 3; printf("Expressions evaluate to: %d and to %f\n", a/d, a/3.0 ); return 0; }