Doodles Do Algebra – Lesson 10


Update: This Lesson Is Part of Book 1 of Doodles Do Algebra: “Starting Out With Mental Algebra” available on Amazon.


Teacher’s Notes:

Today is a review day for your child to practice the last 4 lessons, brought to you by DoodlePig.



Available in the book, “Starting Out With Mental Algebra, Book 1 of Doodles Do Algebra”



  1. This problem walks your child through the process of solving how many oranges, peaches, and lemons Tom purchased. So if he bought an equal number of each type of fruit, and we say that is “x”, or the unknown variable, then the total price of peaches was 2 cents times “x” peaches. Then the total price of oranges was 4 cents times “x” oranges, and the total prices of lemons was 3 cents times “x” lemons. You add 2x + 4x + 3x together to get 9x, and that equals the total price of 45 cents paid for the whole pile of fruit. So if 9x = 45, x = 5. That means that Tom bought 5 of each type of fruit.
  2. Now your child gets to do a problem that is abstract. It is not about buying fruit or how old people are, but just simply numbers. If the first number is x, and the larger exceeds the smaller by 15, then the second number is x+15. The Sum of the two numbers is 25 and equals x plus x+15. So solving for x, 25 = x + x + 15, or 25 = 2x + 15, or 25-15 = 2x, or 10 = 2x, and finally x=5.


I hope that you and your child are enjoying these algebra pages. The next book will be out soon. In the meantime you can get all the information in the upcoming lessons as well as worksheet downloads for pages that have not yet been published on this site.

As always, I welcome feedback.