Look at these number bricks.

You'll notice that 5 + 7  = 12    and that A must equal 10, so that 5 + 10 = 15

The same rule applies with algebra.

So here, the values on the two bricks at the bottom will add to give us the value in the brick above them.

To find the total of these two values, we need to gather like terms:

x + 3 + x - 4 = 2x - 1

In this activity, the expression on any brick can be worked out by adding the expressions on the two bricks below it.

Does this make sense?

Don't worry if you feel like the girl in the picture - we'll work through some together to make sure it becomes clear! Let's get started.