a. 9x^4y^9
It is a monomial and the degree is the sum of the exponents , which is 9 + 4 = 13.
b. x^4 - 3x^2 + 7x^5
It is a trinomial ( 3 terms) and to find the degree you must compare the exponents of each term, as the exponent of the last term is 5 (greater than the other (4 and 2) ) the degree of the polynomial is 5
c. 19a^6b^2 + 8ab^3 + 27a^7
It is a trinomial ( 3 terms) and to find the degree you must compare the exponents of each term.
First term: 6 + 2= 8
Second term: 1 + 3 + 1 = 5
Third term: 7
Since the sum of the exponents of the first term is greater than the sum of the other two terms, the degree of the polynomial would be 8