Final answer:
In the sentence, the correct verb form for 'Mi hermana y mi madre' is 'saben'. The verb form 'sé' is used for 'yo'.
Step-by-step explanation:
In the sentence, 'Mi hermana y mi madre saben tocar la guitarra. Pero yo sé tocar', the correct verb form for the subject 'Mi hermana y mi madre' is 'saben'. The verb form 'saben' is used because the subject is plural (referring to multiple people). The verb form 'sé' is used for the singular subject 'yo'.
Learn more about Spanish verb conjugation