Answer:
Here the degree of the polynomial is 11.
Step-by-step explanation:
To find the degree of the multivariate polynomials, we need to add up the powers of all the variables. So the total degree is given by the sum of all the powers of the highest powers terms.
Now in the given polynomial 
the term with the highest total powers is
and thus the total power is 6+5=11.
And hence the degree of this polynomial is 11.
2.6 because you substract
This looks like scalar matrix multiplication. The idea here is to multiply the scalar 3 by each item inside the matrix.
Doing so leads to the answer [3 -12 15 -21]
Side note: I'm assuming the matrix given to you has 1 row and 4 columns.
The answer is 81.
Hope this helps.