1. Straight lines are 180 degrees. That means 180-126=x. So, x=54.
You can then use x to find y. 180-54=y. y=126. OR You can use vertical angles to find y. Vertical angles are the same degree. So if y is vertical to the angle with 126 degrees, then y=126.
Either way, you will get x=54 and y=126.
2. You would solve problem 2 the same way as problem 1. I encourage you to try to do it yourself, but here's how you would do it.
180-103=y, so y=77. You can either use vertical angles or x=180-77 to find x. You will end up with x=103.
So y=77 and x=103.
3. Here you would use vertical angles. Remember, vertical angles have the same degree! So 2x+29=5x+20. Then all you have to do is solve it.
You would end up with x=3.
I hope that helps!