Question

1. Pass to passive voice:

a) archaelogists often Discover ancient coins.

B) they grow coffee in Brazil.

2. pass to active Voice:

a) exercises are done by the children

b) the subject is explained by the teacher.

Answer 1

1)a) Ancient coins are often found by archaeologists
b)Coffe is grown by them in Brazil

2)a)Children don't do exercises
b)The teacher explains the subject 

Espero ter ajudado ;)