Hello. I wanted to start GTK+ application programming and I was following this tutorial: http://developer.gnome.org/gtk-tutorial/2.90/c39.html

When I run
pkg-config --cflags --libs gtk+-2.0
I get the following error
Package gtk+-2.0 was not found in the pkg-config search path.
Perhaps you should add the directory containing `gtk+-2.0.pc'
to the PKG_CONFIG_PATH environment variable
No package 'gtk+-2.0' found
Please help.

Incidentally, can we also use gtk+-3.0 to create apps in Quantal?