Explain how to evaluate algebraic expression
given value of a variable.

If you are given the value of a variable, all you have to do is substitute the variable for the value. For instance, if you are given an expression 2x + 5y, where x = 4 and y = 2, you evaluate the expression by substituting x with 4 and y with 2. That gives you 2(4) + 5(2) = 8 + 10 = 18

I hope this helps. Please make my answer the brainliest if you are satisfied with it.