For the sentence, "Reading and writing are Fred's favorite thing to do," it's important to know its structure or "anatomy" before we are able to answer the question of what the subject is. Every complete sentence is composed of two parts: the "subject" and the "predicate." The "subject" of a sentence is its topic, whether a person, thing, or concept, and it is usually placed at the beginning of a sentence. The "predicate" is essentially everything else - the verb, object, and other complements. So, with this in mind, let's look at an example: "Math is John's worst subject." The subject, in this case, would be "Math," and the predicate would be the verb "is" plus the the rest of the sentence. Relating this back to the sentence you are dealing with, see which part of the sentence would make the most sense as its "subject." I hope this was helpful, Saraha. Have a nice day!