Step-by-step explanation:
1. Mi amigo es simpático y mi amiga también es simpática.
(My friend is nice and my friend [female] is also nice.)
2. Mi amiga es seria y mi amigo también es serio.
(My friend [female] is serious and my friend is also serious.)
3. Mi amiga es guapa y mi amigo también es guapo.
(My friend [female] is beautiful and my friend is also handsome.)
4. Mi amigo es inteligente y mis amigas también son inteligentes.
(My friend is intelligent and my friends [female] are also intelligent.)
5. Mi amigo es trabajador y mis amigas también son trabajadoras.
(My friend is hardworking and my friends [female] are also hardworking.)
6. Mis amigos son amables y mis amigas también son amables.
(My friends are friendly and my friends [female] are also friendly.)
7. Mi amiga es idealista y mi amigo también es idealista.
(My friend [female] is idealistic and my friend is also idealistic.)
8. Mi amigo es honesto y mi amiga también es honesta.
(My friend is honest and my friend [female] is also honest.)
In each sentence, the adjective in bold is modified to agree with the gender and number of the subject in the second clause. This ensures that the adjective matches the gender and number of the noun it describes. By changing the endings of the adjectives to match the subject, we maintain grammatical agreement.