Help me with this math problem I will give BRAINLIEST for the right answer.
Show your work**

Answer:
The answer is 9x-4.
Step-by-step explanation:
First calculate the area of the backyard. This is 13x-1. Then multiply the area of the patio so multiply x +3 by x+ 3. The answer to this is 4x+3. Next subtract the area of the patio from the area of the backyard. The answer is 9x-4.