Answer:
30.25
Explanation:
All angles of a line must add up to 180. Since we already know that one angle is 90 degrees, we know that the other angles should add up to 90 degrees in order for all of the angles to add up to 180 degrees:
(3x-7)+(x+8)=90
4x+1=90
4x=89
x=22.25
22.25+8= 30.25