If there are several terms in a formula, we can call some of them like terms if they are the same type of term. This happens if they have the same variable.
In the formula a = 8c + 3 - 2c + 5,
8c and -2c are a pair of like terms and 3 and 5 are a pair of like terms.
In the formula p = 3a - 12 + 2b + 4a + 3b + 8,
3a and 4a are a pair of like terms, 2b and 3b are a pair of like terms, and -12 and 8 are a pair of like terms.