- Try some “take away” (subtraction) problems using physical objects (like the base-ten blocks or just fingers).
- Redo the previous activity while making connections with algebraic expressions. For example, “ten take away four equals five” can be written as $10-4=5$.
- Once the child is comfortable with the above activities (this may take some time and practice), practice identifying the terms in $10-4=5$ using the expression such as “$10$ is the original, $4$ is the take-away, and $5$ is the difference” (more technical terms are the minuend, subtrahend, and difference).
- Using physical objects, play with the idea that “the sum of take-away and difference equals the original.” Then connect the idea with the equivalence of the equations $10-4=5$ and $10=4+5$.
- Challenge activity: Prepare an envelope, pen, and some unit blocks (these items can, of course, be replaced with other things). Dad picks up a certain number of blocks, say, $13$. Let the child take away some blocks, say, $4$. Put the difference in the envelope, and mark the envelope with a letter, say, $d$. Remind the child that $4$ and the number of blocks in the envelope add up to $13$. Write the corresponding algebraic equation $4+d=13$. Then let the child hold the $4$ blocks and the envelope, and let her recall the physical reality that the blocks in the envelope is the resultant of $4$ blocks taken away from $13$. Relate the physical reality with the algebraic equation $13-4=d$. Let the child calculate $13-4$ using her favorite method. Let the child write her answer in the form of $d=9$. Now open up the envelope and verify the equality $d=9$.