rmath: 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/rmath - from package: mathomatic

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

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