Ответ:

1. Maths isn't my favourite subject, but I study it

2. Mary and Jack are friends. I go to school with them.

3. Billie Eilish is my favourite singer. I often listen to her.

4. Maths and history are difficult subjects. I study them.

5. German is an interesting language, but I don't speak it.

Объяснение:

в 3ем можно поставить любого исполнителя, если он мужского рода, то her поменять на him

а в 1 и 4 можно поменять названия предметов