These sentences are split into clauses (parts of a sentence), and your assignment is to rewrite the sentences with different ways to connect the two clauses. The example connects the clauses in 3 ways: a comma and "and", a colon, and a period to totally split the clauses.
For the first question, your 3 sentences should be
"Ben ran a good race, and he came in second."
"Ben ran a good race: he came in second."
"Ben ran a good race. He came in second."
The next question:
"We applauded the actress, and she came out for a second bow."
"We applauded the actress: she came out for a second bow."
"We applauded the actress. She came out for a second bow."
Just do this for the next two, and you should be good!