According to the information given in the exercise, the following expression represents the area of the rectangular garden:
And the following expression represents the combined area of the walkway around the rectangular garden and the area of the garden:
You can identify that the word "combined" indicates that that expression was obtained by adding both areas.
Knowing the above, you can set up the following equation:
Where "A" is the area of the walkway around the rectangular garden.
Solving for "A", you get the following expression:
The answer is: