Hi there!
In order to solve this problem, we'll need to use the fact that a triangle's interior angle measure is 180 degrees. We can use this to find x because we can subtract the given angle measurements from 180 to find x.
WORK:
x = 180 - 105 - 40
x = 75 - 40
x = 35 degrees
Hope this helps!! :)
If there's anything else that I can help you with, please let me know!