Doodles Do Algebra – Lesson 36


Update: This Lesson Is Part of Book 3 of Doodles Do Algebra: “The Basic Math of Algebra” available on Amazon.



Available in the book, “The Basic Math of Algebra, Book 3 of Doodles Do Algebra“


This lesson starts the concept of addition in algebra. The basic idea your child needs to grasp is that you add like kinds only. So 2x plus x is two x’es plus one x and you have a total of 3 x’es. But you cannot add x and y because they are fundamentally different variables. You don’t know what they are in terms of numbers so you cannot possibly add them together at this point. What if x was 5 and y was 9? If you added x and y to get, say, 2x then you would have a final answer of 10 instead of 14, assuming x was 5 and y was 9. This is kind of a confusing and simplistic way of explaining, but it is worth putting out there in case your child’s mind works that way. My kids always understood the explanation of adding like kinds (apples to apples and oranges to oranges). Either way, the problems really just boil down to a review of addition of positive and negative numbers, once your child understands the principle.


  1. 12a
  2. 17a^2
  3. 3a+4b
  4. 14a^2b
  5. -14a^2b
  6. 14xy
  7. -14xy
  8. -14xy