When you opened Brasero, did you select Burn an Image as your project type?
After selecting your .iso file and the disk to burn to, did you select Properties and change the burn speed to its lowest setting?
I'm sorry if these seem too simple, but I don't know your level of competence in this task.
LMDE Mate 64-bit, LM17.3 Cinnamon 64-bit
Debian Mate 64-bit, Xubuntu xenial 64-bit, Ubuntu-Mate 14.04 64-bit, Antergos Xfce 64-bit, PCLinuxOS Mate 64-bit