I have a back pack leaf blower. My son accidentally put half and half which is antifreeze in it instead of gas. Now we can't get it to start, he emptied out the antifreeze and put in regular gas, and tried, but no luck. Any ideas?

At the very least you will need to remove and clean the spark plug. Make sure the antifreeze is out (especially out of the carb) and eventually it should start if you have a little bit of luck on your side.

You will need to completely clean out the entire fuel system. That means carb, fuel lines and gas tank. Wasn't the container marked?