Here is one way to write the same letter three times: n + n + n. Is there a neater way to write three of the same letter added together?

Think of each x as a bag with an unknown number of cubes inside, and each plain number as loose cubes on the table.

Watch three expressions get tidied up. Each board is captioned with the algebra it is showing, so you can see the bags and the expression at the same time.

Key point Only like terms can be combined. Bags join with bags because they hold the same unknown amount. Loose numbers join with loose numbers. A bag and a loose number are not like terms, so they can never be pushed together into one term.

Before each answer appears, predict which terms are alike and which have to stay apart.

Sort the scattered cards into two groups. Put the x-bags (the x-terms) in one place. Put the loose cubes (the plain numbers) in the other. The cards on screen are 5x, 2, 3x, x and 4. When they are sorted, say the simplified expression aloud.