This is the concept of geometry, to calculate for the length EB we proceed as follows;
Given that ABCD is a parallelogram, AE=EC and DE=EB
but
AE=p-8, CE=2p-58
thus;
p-8=2p-58
calculating for the value of p we get:
p-2p=-58+8
-p=-50
thus
p=50
hence the value of EB will be:
EB=DE
DE= p+15
substituting the value of p we get:
DE=50+15=65
thus;
DE=EB=65
The answer is EB=65