Unable to run fsk (to solve boot problem)

After updating Xubuntu 18.04 I am suddenly unable to boot my dual-boot PC.

The error message I get when I try to boot in recovery mode is:

/dev/sda5: UNEXPECTED INCONSISTENCY; RUN fsk MANUALLY
…
fsk exited with status code 4
done.
Failure: File system check of the root filesystem failed
The root filesystem on /dev/sda5 requires a manual fsck
BusyBox v1.27.2 (Ubuntu 1:1.27.2-2ubuntu3) built-in shell (ash)
Enter ‘help’ for a list of built-in commands.
(initramfs) _

I have unsuccessfully attempted to run fsk at the prompt as shown below.

(initramfs) fsk /dev/sda5
sh: fsk: not found

I got the same result trying to run fsk after switching to the /sbin directory.

(initramfs) cd sbin
(initramfs) fsk /dev/sda5
sh: fsk: not found

Another thing that I tried was to boot using a live USB drive. However this failed to work. As the PC boots using the live USB drive, it hangs up. Specifically, when the solid colored Xubuntu background page appears during boot, there is a spinning icon; this is where the system hangs.

I do not know what to try next. Any suggestions would be much appreciated!

Thanks,
Kevin