Be; short answers. complete the questions and write the short answers. good at geography? 3 brilliant at maths? and your friends all thirteen? and mark brother and sister?

1 Is Jack good at geography?  No, he isn't.
3 Are you brilliant at Maths?  No, I am not
4 Are you and your friends all thirteen?  Yes, we are.
5 Are Ann and Mark brother and sister? Yes, they are.