The statement is True.
An algebraic expression can be evaluated to find its numerical value by substituting specified numerical values for each variable in the expression. For example, if you have an expression like \(2x + 3y\) and you are given \(x = 2\) and \(y = 4\), you can find the value of the expression by substituting these values in:
\[ 2(2) + 3(4) = 4 + 12 = 16. \]
Thus, evaluating an algebraic expression by substituting values for its variables is a fundamental concept in algebra.