Hallo runix, ich habe es in etwa so gemacht: \documentclass[a4paper,10pt]{scrreprt} \usepackage[utf8]{inputenc} \usepackage{amsmath}[2000/07/18] \usepackage{amssymb}[2002/01/22] \usepackage[disallowspaces]{mathtools} \usepackage[detect-all, locale = DE]{siunitx} \begin{document} \begin{alignat*}{2} r^2 &= (\SI{15}{\cm})^2 + a^2\\ r^2 &= (\SI{15}{\cm})^2 + (r - \SI{5}{\cm})^2\\ r^2 &= \SI{225}{\cm^2} + r^2 - r\SI{10}{\cm} + \SI{25}{\cm^2} &&\bigg\vert - r^2\\ 0 &= \SI{250}{\cm^2} - r\SI{10}{\cm} &&\bigg\vert + r10\\ r\SI{10}{\cm} &= \SI{250}{\cm} &&\bigg\vert : 10\\ r &= \SI{25}{\cm}\\ A_\text{Halbkreis} &= \dfrac{1}{2}(\pi r^2) &&\bigg\vert (\approx \SI{3,14} * \SI{625}{\cm\squared}) : 2 \\ A_\text{Halbkreis} & \approx\SI{981,75}{\cm^2} \end{alignat*} \end{document} Viel Erfolg Gruß Martin \documentclass[a4paper,10pt]{scrreprt} \usepackage[utf8]{inputenc} \usepackage{amsmath}[2000/07/18] \usepackage{amssymb}[2002/01/22] \usepackage[disallowspaces]{mathtools} \usepackage[detect-all, locale = DE]{siunitx} \begin{document} \begin{alignat*}{2} 3 \cdot x &= 4 \cdot x + x\bigg\vert -x\\ 2 \cdot x&= 4 \bigg\vert : 2\\ x&= 2 \end{alignat*} \end{document}

Hallo runix, ich habe es in etwa so gemacht: \documentclass[a4paper,10pt]{scrreprt} \usepackage[utf8]{inputenc} \usepackage{amsmath}[2000/07/18] \usepackage{amssymb}[2002/01/22] \usepackage[disallowspaces]{mathtools} \usepackage[detect-all, locale = DE]{siunitx} \begin{document} \begin{alignat*}{2} r^2 &= (\SI{15}{\cm})^2 + a^2\\ r^2 &= (\SI{15}{\cm})^2 + (r - \SI{5}{\cm})^2\\ r^2 &= \SI{225}{\cm^2} + r^2 - r\SI{10}{\cm} + \SI{25}{\cm^2} &&\bigg\vert - r^2\\ 0 &= \SI{250}{\cm^2} - r\SI{10}{\cm} &&\bigg\vert + r10\\ r\SI{10}{\cm} &= \SI{250}{\cm} &&\bigg\vert : 10\\ r &= \SI{25}{\cm}\\ A_\text{Halbkreis} &= \dfrac{1}{2}(\pi r^2) &&\bigg\vert (\approx \SI{3,14} * \SI{625}{\cm\squared}) : 2 \\ A_\text{Halbkreis} & \approx\SI{981,75}{\cm^2} \end{alignat*} \end{document} Viel Erfolg Gruß Martin