standard_description: Identify when two expressions are equivalent (i.e., when the two expressions name the same number regardless of which value is substituted into them). For example, the expressions y + y + y and 3y are equivalent because they name the same number regardless of which number y stands for.
problem_activity: Task
To compute the perimeter of a rectangle you add the length, $l$ and width, $w$ and double this sum.
Write an expression for the perimeter of a rectangle.
Use the expression to ﬁnd the perimeter of a rectangle with length 30 and width 75.


aligns: no