Explanation:
First of all we have to change the sign after the sign of subtraction.
(x^2+2x-3)-(x^2+3x+5)
now,
=x^2+2x-3-x^2-3x-5
after changing sign,we should put it by arranging.
=x^2-x^2+2x-3x-3-5
=-x-8
again,
Degree of -x=1
Hence,the degree of polynomial is one.