standard_description: Write, read, and evaluate expressions in which letters stand for numbers.
problem_activity: Task
A numeric expression like $5+(8 + 2)^2$ has one and only one value. What is it?
Consider the expression $5+(x + 2)^2$. What are some values it can have? Make sure you organize your work, so anyone can tell which value for the expression goes with which $x$ value.
How many different values can an algebraic expression like $5+(x + 2)^2$ have?
What is the difference between the expression $2x$ when it is all by itself and when it is in an equation like $2x = 12$ ?


aligns: yes