kalgebra: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/kalgebra - from package: kalgebra

You may install the required package with command apt-get install {package}

Error in other languages:
kalgebra: bevel nie gevind nie
kalgebra: comandă negăsită
kalgebra: comando não encontrado
kalgebra: commande introuvable
kalgebra: command not found
kalgebra: käsku ei ole
kalgebra: không tìm thấy lệnh
kalgebra: komanda nerasta
kalgebra: Kommando nicht gefunden.
kalgebra: kommandot finns inte
kalgebra: komut yok
kalgebra: nie znaleziono polecenia
kalgebra: níor aimsíodh an t-ordú
kalgebra: no se encontró la orden
kalgebra: no s'ha trobat l'ordre
kalgebra: opdracht niet gevonden
kalgebra: parancs nem található
kalgebra: perintah tidak ditemukan
kalgebra: príkaz nenájdený
kalgebra: příkaz nenalezen
kalgebra: команда не найдена
kalgebra: командата не е открита
kalgebra: 命令找不到
kalgebra: コマンドが見つかりません