Answer:
135°
Explanation:
Assuming the lines are straight you can assume the angle of a straight line is 180, but these lines are cut.
but you can still say the angles b+a=180.
b is in this equation, but before we can find it, we are going to have to find a.
You can do this for the other line as well: 3a + a = 180
4a = 180
a=45
now just plug that back in
b+45=180
b= 135