Answer:
90
Step-by-step explanation:
c is perpendicular to b
That means angles 5,6,7,8 are 90 degrees
a is parallel to c
That means b is perpendicular to a
That means that 1,2,3,4 are 90 degrees
<1 = 90 degrees
the answer is 90
simpliy because c and b make a right angle
