Используем свойства степеней: \( a^m \cdot a^n = a^{m+n} \), \( a^m : a^n = a^{m-n} \), \( (a^m)^n = a^{m \cdot n} \).
\( x^8 \cdot x^3 = x^{8+3} = x^{11} \)
\( x^{19} : x^{12} \cdot x = x^{19-12} \cdot x = x^7 \cdot x^1 = x^{7+1} = x^8 \)
\( (x^9)^4 : x^{26} = x^{9 \cdot 4} : x^{26} = x^{36} : x^{26} = x^{36-26} = x^{10} \)
\( \frac{x^{24} \cdot x^9}{(x^7)^2} = \frac{x^{24+9}}{x^{7 \cdot 2}} = \frac{x^{33}}{x^{14}} = x^{33-14} = x^{19} \)
Ответ: а) \( x^{11} \); б) \( x^8 \); в) \( x^{10} \); г) \( x^{19} \).