State whether the following expression is a numerical expression or an algebraic expression.

$11a^2+6b^2-5$

State whether the algebraic expression given below is monomial, binomial, trinomial or multinomial.

$a^2+b^2$

Find the degree of the algebraic expression $2y^{2}z+9yz-7z-11x^2{y}^2$?

Find the degree of the algebraic expression $pq+p^{2}q-p^2{q}^2$?

If we subtract the first term from the second term in $5a^2,10a^2$ we get $k{a}^2$, then find the value of $k$.