Answer: 
<u>Step-by-step explanation:</u>

Answer:1/2
Step-by-step explanation:
Answer:
To find the missing side we need to calculate the sum of the two given sides and then subtract that from the perimeter.
7a - 11b - (2a + b + a - 9b)
= 7a - 11b - (3a - 8b)
= 7a - 3a - 11b + 8b
= 4a - 3b