The associative property applies only to the operations of addition and multiplication. It basically tells us that the order of numbers or how the numbers are grouped does not matter because the sum or product will be the same. This does not apply to subtraction because obviously the output of subtracting two numbers is dependent on which way they are arranged.
These worksheets explain how to rewrite equations using the associative properties of addition and multiplication. Instructors, note that answers will only be in the form of equations.