The best way to install Inkscape is by using the Ubuntu Sotware Center.
Simply open Software Center and search on GIMP
Click on install and follow the process to install GIMP on your system.
You can also install GIMP via PPA
Open terminal from system application launcher. When it opens, run command to add the PPA:
sudo add-apt-repository ppa:ubuntuhandbook1/gimp
Type user password (no asterisk feedback) for sudo prompts and hit Enter to continue.
After it completes run the following apt commands in terminal to install GIMP:
sudo apt update sudo apt install gimp gimp-gmic