1. Apply the distributive property to expand $(-9p)(-10+3p)$:
(-9p)(-10) + (-9p)(3p) = 90p - 27p^2
2. Apply the distributive property to expand $7p(-9+3p)$:
7p(-9) + 7p(3p) = -63p + 21p^2
3. Combine like terms:
(-27p^2 + 21p^2) + (90p - 63p) = -6p^2 + 27p
4. Therefore, the answer is:
-6p^2 + 27p