Answer:
p=6
Explanation:
triangles add up to 180 degrees, and a right angle =90 degrees. 
from there, we can do 180-90=90 degrees then do 90/15=6. p =6
(we divide by 15 because 7+8=15)
 
to check, we see if all angles add up to 180. 
7×6=42 8×6=48 right angle=90
42+48+90=180