Simple Equations as Introduction to Algebra

A good place to start is manipulating a simple equation to discover a missing number as in:

Next practice is to show that an value on the left of an equation is equal to what is on the right,

i.e. 4 + 3 = 2 + 5.

Have them complete the sheets on finding the missing number on these sheets:

Finally a few equations replace the blank line with a letter, introducing them to using letters to represent an unknown.