Final answer:
To declare the 'number_of_children' variable, use 'int number_of_children;' in Computer Science.
Step-by-step explanation:
To declare a variable named number_of_children that can hold the number of children in a family, you can use the syntax:
int number_of_children;
This declares a variable of type int (integer) named number_of_children. The variable can store whole numbers (including negative numbers) such as 0, 1, 2, etc.
For example, to assign a value to this variable, you can use:
number_of_children = 3;
This assigns the value 3 to the number_of_children variable.