To declare variables in C, you use the following syntax: ```c data_type variable_name; ``` For example, to declare an integer variable called age, you would do the following: ```c int age; ``` Here are some examples of how to declare variables in C for different data types: ```c int age; // Integer variable to store age float height; // Floating point variable to store height char letter; // Character variable to store a letter double salario; // Double precision floating point variable to store salary ``` You can also initialize variables during the declaration: ```c int numero = 10; // Integer variable initialized to 10 float pi = 3.14; // Floating point variable initialized to 3.14 char letra = 'A'; // Character variable initialized with the character 'A' ``` In addition, in C, you can declare and initialize several variables of the same type on a single line, separating them with commas: ```c int a, b, c; // Integer variables a, b and c a = 1; b = 2; c = 3; ```