1) $$x^{11} : x^7 \cdot x^3 = x^{11-7} \cdot x^3 = x^4 \cdot x^3 = x^{4+3} = x^7$$
2) $$-2a^7b \cdot (-3)a^4b^9 = -2 \cdot (-3) \cdot a^{7+1} \cdot b^{1+9} = 6a^8b^{10}$$
3) $$(-3a^3b^2)^4 = (-3)^4 \cdot (a^3)^4 \cdot (b^2)^4 = 81a^{3 \cdot 4}b^{2 \cdot 4} = 81a^{12}b^8$$
Ответ: 1) $$x^7$$, 2) $$6a^8b^{10}$$, 3) $$81a^{12}b^8$$