Answer:
Step-by-step explanation:
You could do it either way, but I have attached an image with one way to do it.
Then, using the exterior angle theorem, you can do:
(180-4x) + 100 = 3x
280 - 4x = 3x
280 = 7x
x = 40
From there, don't forget to plug in the numbers if you need to do so :)
