qsolve: 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 CentOS possible default full paths are:

/usr/lib64/4ti2/bin/qsolve - from package: 4ti2

You may install the required package with command yum install {package}

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