What must be subtracted from $4p^2-2pq-6q^2-r+5$ to get $-p^2+pq-8q^2-2r+6$?

Add:

$4x^2–7xy+4y^2–3, 5+6y^2–8xy+x^2$ and $6–2xy+2x^2–5y^2$

Add: $8ab, -5ab, 3ab, -ab$

Subtract $–8pq$ from $6pq$

Add: $7x, -3x, 5x, –x, -2x$

Subtract $–16p$ from $–11p$

Add: $6ax–2by+3cz, 6by-11ax–cz$ and $10cz-2ax–3by$

Subtract:

$2a^{2}b$ from $–5a^{2}b$

Add: $\left(5x–8y+2z\right)+\left(3z–4y–2x\right)+\left(6y–z–x\right)+\left(3x–2z–3y\right)$

Add:

$2x^3–9x^2+8, 3x^2–6x-5, 7x^3–10x+1$ and $3+2x–5x^2–4x^3$

Subtract $4a^2+5b^2-6c^2+8$ from $2a^2-3b^2-4c^2-5$

Subtract:

$2a–5b+2c–9$ from $3a–4b–c+6$

Add: $6p+4q–r+3, 2r-5p–6, 11q-7p+2r–1$ and $2q–3r+4$

Subtract: $–6p+q+3r+8$ from $p–2q–5r–8$

Subtract:

$x^3+3x^2–5x+4$ from $3x^3–x^2+2x–4$

Add: $3a–4b+4c, 2a+3b–8c, a–6b+c$

Subtract $–2abc$ from $–8abc$