Find the degree of $5-9y+15y^2-6y^3$.

Find the degree of $u^5+u^{4}v+u^3{v}^2+u^2{v}^3+u{v}^4$.

Add and find the degree of $(9x+3y)$ and $(10x-9y)$.

Add and find the degree of $\left(k^2-25k+46\right)$ and $\left(23-2k^2+21k\right)$

Add and find the degree of $\left(3m^{2}n+4p{q}^2\right)$ and $\left(5n{m}^2-2q^{2}p\right)$. 

Simplify and find the degree of $10x^2-3xy+9y^2-\left(3x^2-6xy-3y^2\right)$.

Simplify and find the degree of $9a^4-6a^3-6a^4-3a^2+7a^3+5a^2$.

Simplify and find the degree of the expression.

$4x^2-3x-\left[8x-\left(5x^2-8\right)\right]$