Final answer:
To simplify expressions with variables and coefficients, combine like terms by adding or subtracting their coefficients and leave the variable unchanged.
Step-by-step explanation:
a) 23p - 7p:
To simplify this expression, we need to combine like terms. Like terms have the same variable and exponent. In this case, the like terms are the terms with 'p'. So, we have 23p - 7p.
Combining the coefficients of the like terms, we get (23 - 7)p. Subtracting 7 from 23, we get 16. Therefore, the simplified expression is 16p.
b) 3ab - 9ab + 7ab:
To simplify this expression, we need to combine like terms. Like terms have the same variables and exponents. In this case, the like terms are the terms with 'ab'.
Combining the coefficients of the like terms, we get (3 - 9 + 7)ab. Adding 3 and 7, and subtracting 9, we get 1. Therefore, the simplified expression is ab.