1 Those shoes are quite cheap. They're unexpensive.
2 Your answer is wrong. It's incorrect.
3 My sister is very sad. She's unhappy.
4 Our new house isn't finished. It's incomplete.
5 Her clothes aren't very modern. They're unfashionable
6 Williarn never says hello. He's unfriendly.
7. The price doesn't matter. It's unimportant.