Answer:
Degree = -1*
Explanation:
The degree of a polynomial is its greatest exponent among all its terms.
To begin we group equal terms and solve the sums.

Resolving the sums we have to:
P (x) = 0
This polynomial is considered a null polynomial.
There are several opinions about the degree of a null polynomial.
Some books consider it as -infinity, others say it is not defined.
On the other hand, some assign a grade -1 by convention *
* [Hernandez Ruiperez, Daniel (1990). Linear algebra. Salamanca, Spain. Pag. 41]