You need to declare your variables using the form: [optional modifiers] [type] [name] = [value]; for example, "const char* string = 'hello\n';"

Step 1: Your type is double and your value is 100.

Step 2: Same process again, only it has to be made constant.

Step 3: You don't have to hardcode your values in variable assignment and you can perform calculations in the process. You can easily assign the value 100*30 to a variable or assign something like length*height, where length and height are predeclared.