This is the gentlest introduction to algebra you'll find anywhere! Students are given an addition number sentence (an equation) with a missing value (in lieu of a variable) that they must find.
theyse pre-algebra addition worksheets present number sentences with missing values that students fill in. This is a way to introduce the concent of 'missing' values in an equation without the letter variable notation.
Even though algebra concepts are usually introduced until later, these types of problems are based on very simple arithmetic that can be understood by 2nd or 3rd graders, and these worksheets can be used along the process of learning the basic addition facts as well. You might even be able to sneak an 'x' in there along the way!