1. Anybody could do the sum as it was very easy. 2. Did you watch interesting on
TV yesterday? 3. knew the answer to the question. 4. Ann was so sad yesterday
that interested her. 5. I’d like to do exciting today. 6. wants to do
the project with Mary. Will you help her, Jim? 7. Aunt Mary is moving to a new house.
must help her. 8. Helen speaks English so well. understands her.
9. If is clear to you, start writing the test. 10. Would you like to watch
funny in the cinema? 11. Is there inside? 12. Mike understood because of
the noise.

1. Anybody could do the sum as it was very easy. Anybody refers to any person, so the correct form of the verb should be "could" instead of "can" or "could have done". We use "could" to express ability in the past. The phrase "do the sum" means to solve the calculation. 2. Did you watch interesting on TV yesterday? The word order in the sentence is incorrect. We should say "Did you watch something interesting on TV yesterday?" The word "something" is needed to make the question grammatically correct. 3. knew the answer to the question. The sentence is grammatically correct. The word "knew" is the past tense of "know", which means to have information or be aware of something. 4. Ann was so sad yesterday that interested her. The verb form "interested" is incorrect in this sentence. The correct form should be "it interested her." The word order needs to be changed to make the sentence grammatically correct. 5. I’d like to do exciting today. The sentence is grammatically correct. The word "exciting" is an adjective that describes something that causes excitement or interest. 6. wants to do the project with Mary. Will you help her, Jim? The sentence is grammatically correct. The word "wants" is the present tense form of the verb "want", which expresses a desire or a wish. 7. Aunt Mary is moving to a new house. must help her. The word "must" should be changed to "We must" in order to make the sentence complete and grammatically correct. 8. Helen speaks English so well. understands her. The verb form "understands" is incorrect in this sentence. The correct form should be "I understand her." The word "I" is needed to complete the sentence. 9. If is clear to you, start writing the test. The word "If" should be changed to "It" to make the sentence grammatically correct. The correct form should be "If it is clear to you, start writing the test." 10. Would you like to watch funny in the cinema? The word "funny" should be changed to "something funny" to make the sentence grammatically correct. The correct form should be "Would you like to watch something funny in the cinema?" 11. Is there inside? The word "inside" is incomplete in the sentence. We need to specify what is inside. The correct form should be "Is there something inside?" 12. Mike understood because of the noise. The sentence is grammatically correct. The word "because of" is used to indicate the reason or cause of something.