Evaluate an expression with one variable ex 1, x + 5; x = 3

The video tutorial begins with a simple math problem, evaluating the expression X + 5 when X equals 3. The teacher explains the concept of variables as unknowns and demonstrates how to assign a value to a variable. By substituting the value of 3 for X, the expression becomes 3 + 5, which is then solved to give the result of 8. The tutorial emphasizes understanding variables and basic arithmetic operations.

Explain the concept of variables as unknowns in mathematics.

Why is it important to evaluate expressions with assigned values?