Oh no, GRUB kicked the bucket! Luckily for you, your professor just went over Frankenstein last week, so you can say that you're somewhat of an expert with reviving the dead. :^)
1 - Boot into a live Linux disk
2 - Open a terminal: ( {key CTRL} + {key ALT} + {key T} )
3 - Become root `sudo su`
4 - Run `fdisk -l` to find out where Linux is installed in the drive you're working on. It should look something like so: {F1988} in this case, the drive that Linux is installed on is `/dev/sda`, and the partition is `/dev/sda3`
5 - Now to mount our Linux filesystem: `mount /dev/sdxX /mnt`
//**NOTE:** in this example, you would mount /dev/sda3//
```
mount --bind /proc /mnt/proc
mount --bind /sys /mnt/sys
mount --bind /dev /mnt/dev
```
6 - Now we want to work inside of what we've mounted, ergo: `chroot /mnt`
7 - Reinstall GRUB:
```
grub-install /dev/sdX
grub2-install /dev/sdX
```
//**NOTE:** in this case, we're installing it to /dev/sda//
8 - Unmount everything previously mounted:
```
umount /mnt/proc
umount /mnt/sys
umount /mnt/dev
umount /mnt
```
9 - Revel in the fruits of your labor and `reboot`