Как правильно my friends` posters is nice или my friends` posters are nice?

Правильно my friends' posters is nice. потому что "друзья" множественого числа.

My friends posters are nice

1. it is important to understand a. why any organization should have internal auditing.2. what happens b. when your balance sheet does not balance? 3. one of the most important lessons to learn a. if you want financial success is the difference between assets and liabilities.4. the lecturer explained to us c. how banks do business and earn profits.5. current account transactions represent a common banking service c. which has not varied substantively over hundreds of years of bank-and-client relations.по-моему так.

1. she stayed locked in her room, refusing to come downstairs. 2. he had a good practical knowledge of the language,  having worked as an interpreter for many years. 3. they went out as they had come,  seeing nobody and  seen by no one on their way. 4. except for the grand piano and the pianist  sitting before it, the stage was empty. 5. he looked so beautiful and peaceful, sat in that chair under the tree. 6. he looked at the scene  shaken to the depth of his heart. 7. the boy came out of the water, all blue and  shaking from head to foot. 8. arriving at the airport where he was to change, he had to wait for three hours for the connection. 9.  having arrived in the town about twenty years before, he had succeeded thereafter beyond his wildest expectations. 10.  supported by her elbow, mary listened to their talk. 11. supporting her by his arm, he helped her out of the carriage. 12. the girl was fascinated by the dark surface of the water  reflecting the stars. 13. the young foliage of the trees, reflected in the river, looked like lace. 14.1 saw the figure of an old woman coming towards me. 15. my brother is a soldier having just  come back home on leave.