Final answer:
The subject 'Sequoia and Charles' and the verb 'plans' do not agree in the original sentence. The revised sentence 'Sequoia and Charles plan to exercise together' corrects the agreement error.
Step-by-step explanation:
In the sentence 'Sequoia and Charles plans to exercise together', the two elements that do not agree are the subject 'Sequoia and Charles' and the verb 'plans'. The subject should be plural, so the verb should also be plural. The revised sentence that corrects the agreement error is: 'Sequoia and Charles plan to exercise together'.