The issue in this sentence is parallel construction. Each item in a list must be formatted in the same way, but in this sentence, two of these items are gerunds ("buying" and "eating") and the third is a noun ("fun"). So, "fun" contains the sentence's error. The sentence could be corrected by changing "fun" to "having fun."

This sentence contains is an error in parallelism. The sentence lists three things that the subject, Clark, did:

1. bought a leather jacket
2. learned to ride a motorcycle
3. listens to classic rock 

These three phrases must have parallel structure. The first two phrases start with past-tense verbs, "bought" and "learned," so the last phrase should start with a past tense verb too. That means that to correct the sentence, "listens" should be changed to "listened."

This sentence's error is faulty parallelism. The first two of the three things listed as Roosevelt's hobbies are presented in the form of gerunds, verbs that end ing "-ing" and act as nouns. The third hobby should follow the previous examples and be written as "writing about history" instead of "wrote about history."  

This sentence has an error in parallelism.

Here, the money Cherie would win would provide funding for three things: ingredients, rent, and publicity. Imagine the sentence this way:

"Winning $10,000 would help Cherie build her cupcake business by providing the funds she needs for [ingredients], [rent], and [to afford publicity]."

The three objects at the end of the sentence are what she needs funding for, so try expanding the sentence to see if it makes sense:

"providing the funds she needs for ingredients, (for) rent, and (for) to afford publicity."

The final prepositional phrase isn't necessary, since "for" already applies to "publicity." Instead, only the noun "publicity" is needed, as the other two objects are nouns, as well. The correct sentence should be:

"Winning $10,000 would help Cherie build her cupcake business by providing the funds she needs for ingredients, rent, and publicity."

This sentence makes a mistake in parallelism. The conjunction that correctly goes with the conjunction "neither" is "nor," not "or." "Either" and "or" are used together, and "neither" and "nor" are used together. The rest of the sentence is correct as is.

The forms of verbs used in a list need to agree for the sentence to use proper parallelism. Because the sentence begins its list of two items with "creating," "reduce" should be changed to "reducing" in order to match the form of "creating." So, the corrected sentence would read, "Important things to remember when adding fractions include creating a common denominator and reducing."

The elements in the list should have a parallel grammatical structure. Since the first two use infinitive verbs ("to catch . . . build"), the third should too. The corrected sentence reads, "The final three challenges in the obstacle course were to catch a rabbit, build it an enclosure, and leap over the structure."

The three elements in the list should be formatted in the same way. Since the first two are just nouns without verbals, the third should be too. The corrected sentence reads, "The evening's entertainment consisted of a jazz quartet, a juggler, and a game of musical chairs."

When phrases are enumerated in a list, it is important that the list use parallel structure—that is, it is important that all of the items in the list are presented in the same grammatical form. Here, two of the phrases use gerunds: "dicing" and "baking." We can't change those because they are not underlined, so the phrase "how to spice" should instead be changed to the gerund "spicing."

This sentence contains an error in parallel structure because it does not phrase all of the items in its list consistently. The first two items in the list are nouns ("dexterity" and "precision"), but the third item in the list is a gerund phrase ("being patient"). You could correct this error by replacing "being patient" with "patience."