simple subject of this sentence
Alex Tanner added a spoonful of vanilla
Be sure to read through the exchange in the following post from last night.
http://www.jiskha.com/display.cgi?id=1255487005
Then let us know what YOU THINK the simple subject is. First find the verb; the verb is what someone is DOING in the sentence. Then ask yourself, "Who/What is ______ing?" That will be the subject.
You learn nothing when other people do your work for you all the time.