It looks like you have the wrong keyboard set. The keyboard layout varies in different countries and I have the " on Shift+2; this is the default in the UK.
You were asked what keyboard layout you wanted when you installed but I think it defaults to a UK keyboard. Luckily you don't need to reinstall to change it.
From the Menu select "Preferences" > "Keyboard and mouse"
In the application that opens select the "Keyboard" tab and click lxkeymap as shown
This opens a new window
From here you can select the keyboard layout that matches your computer and select Apply.
Job done, the new setting will be remembered.