$$ \begin{flalign*} & \textbf{Aufgabe 1 } & \\ a) \hspace{1cm} & \15 X + 12 = -18 \\ b) \hspace{1cm} & \13 X + 9 = -22 \\ c) \hspace{1cm} & \6 X + 3 + 21 = 10 - 3 X \\ d) \hspace{1cm} & \-18 X + 3 = -21 \\ e) \hspace{1cm} & \12 X + 3 -21 = 12 X + 3 -21 \\ f) \hspace{1cm} & \5 X + 3 = -21 + -21 X \\ h) \hspace{1cm} & \12 X + 3 + 2X - -21 = 12 X + 3 -21 X + 6 \\ & \textbf{Aufgabe 2} & \\ a) \hspace{1cm} & \-18 X^{2}-\frac{1}{ 9 } X^{3} = 0 \\ b) \hspace{1cm} & \15 X^{2}-\frac{1}{ 15 } X^{2} = 0\\ c) \hspace{1cm} & \ binom{21}{x}\sum_{x}^{x+12} ( X+2X - 12 ) \\ d) \hspace{1cm} & \ X^{3} - 12 X - 12 + -18 X^{2}-\frac{1}{ 9 } x^{2} = 0 \\ e) \hspace{1cm} & \ e) \binom{21}{x}\sum_{x}^{x+12} ( X+2X - 12 ) \\ & \textbf{Aufgabe 3} & \\ \left( 12 a-b\right)^2 + \left(b- 8 \right)^2 + \left( - 15 c - 12 \right)^2 = 0 \\ \left( 9 a-b\right)^2 + \left(b- -22 \right)^2 + \left( - 6 c - 3 \right)^2 = 0 \\ \left( 21 a-b\right)^2 + \left(b- 13 \right)^2 + \left( - 3 c - 3 \right)^2 = 0 \\ \left( 21 a-b\right)^2 + \left(b- 13 \right)^2 + \left( - 3 c - 3 \right)^2 = 0 \\ \end{flalign*} $$