Answer:
a=15, b=14
Explanation:
We know all angles must add up to 360, so lets add all angles and set them equal to 360.

We also know that any angle opposite another is equal. Lets take 6b-42 and 3b and set them equal.

Now solve for b in both equations


Now we set the two equations equal to each other to solve for a:

This gives a=15, b=14.