Final answer:
The expression 10 - 3x + 4y - z has three variables: x, y, and z. Variables are symbols representing unknowns or quantities that can vary.
Step-by-step explanation:
The expression 10 - 3x + 4y - z contains three variables: x, y, and z. To determine the number of variables, we look for different alphabetic characters that represent unknown values or quantities that can change. Here, x, y, and z are distinct variables, making a total of three. It's important to note that variables are symbolic representations, and their values can be determined if we have relevant equations or additional information.