Answer:
We know that (4/5b - 4/5 - 1) / b = 1
Which means that b = 4/5b - 4/5 - 1
So we put variable on one side and numbers on the other side
So 1/5b = - 9/5
So b = - 9
<1=97°
steps:
<1+83=180 co interior angle
<1=180-83=97°