Answer:
[tex]-2a+b[/tex]
Step-by-step explanation:
[tex]\left(11a-8b\right)-\left(13a-9b\right)\\11a-8b-\left(13a-9b\right)\\11a-8b-13a+9b\\11a-13a-8b+9b\\-2a-8b+9b\\-2a+b[/tex]
