Collecting Like Terms Without Mixing Unlike Ones

In algebra, only like terms can be combined. Like terms have exactly the same variable part.

3x + 5x = 8x

Both terms are x terms, so they combine.

4a + 2b

These do not combine, because a and b are different variables.

A longer example

7x + 4 – 2x + 9 = 5x + 13

The x terms combine to 5x and the constants combine to 13.

Common mistake: writing 3x + 2 = 5x. The number 2 is not an x term, so it cannot be merged into 3x.

Useful next step: cover the worked answer and try the same method on a similar question before moving on.