Once addition has been explored a bit, it leads pretty naturally to a new question: if there are three bricks in a pile, how many bricks do I need to add to it so that there will be five in the pile?

Our addition problems were all phrased using a pattern like

number + number = what?

and the question above rearranges it a bit:

number + what? = number

or

what? + number = number

This question is usually asked as “What is the difference between Continue reading Algebra Intro 3: Subtraction