1) $$x^6 \cdot x^8 = x^{6+8} = x^{14}$$
2) $$x^6 : x^2 = x^{6-2} = x^4$$
3) $$(x^5)^8 = x^{5\cdot8} = x^{40}$$
4) $$\frac{(x^4)^3}{x^9} = \frac{x^{4\cdot3}}{x^9} = \frac{x^{12}}{x^9} = x^{12-9} = x^3$$
Ответ: 1) $$x^{14}$$, 2) $$x^4$$, 3) $$x^{40}$$, 4) $$x^3$$