To evaluate a function or an algebraic expression containing a variable, a value is substituted for the variable. For example, the algebraic expression 3x+53x+53x+5 can be evaluated for x=10.x={\color{#0000FF}{10}}.x=10. 3⋅10+5 3\cdot {\color{#0000FF}{10}}+5 3⋅10+5