To evaluate a function or an algebraic expression containing variables, values are substituted for the variables. For example, the algebraic expression 2a+3b2a+3b2a+3b can be evaluated for a=4a={\color{#0000FF}{4}}a=4 and b=1.b={\color{#009600}{1}}.b=1. 2⋅4+3⋅1 2\cdot{\color{#0000FF}{4}}+3\cdot{\color{#009600}{1}} 2⋅4+3⋅1