To simplify algebraic expressions, we collect or group like terms.

Example One - Wildlife Reserve

Imagine a wildlife reserve has antelopes, gorillas, kangaroos and zebras.
Let each animal be identified using a letter such a, g, k, z.

Question 1 In one park of the wildlife reserve, there are 3 zebras, 5 gorillas and 6 kangaroos. A year later, 2 zebras and 3 gorillas are born, but 4 kangaroos died. How many of each animal are there now?

Answer 1 The like terms are the zebras, the gorillas and the kangaroos.
3z + 5g + 6k + 2z + 3g – 4k
= 5z + 8g + 2k

Question 2 In another part of the reserve, there are 2 kangaroos and 5 antelopes. After one year, the population of each group doubled. How many of each are there now?

Answer 2 The like terms are the antelopes and the kangaroos.
(2k + 5a) × 2
= 4k + 10a