Выберете существительное в общем или притяжательном падеже:
l. (The engineers, the engineer's) letters are not this table.
2. (My friend, my friend's) children are small.
3. (My friend, my friend's) is twenty.

1.The engineer's letters are not this table (предлога не хватает )2.My friend's children are small. 3.My friend is twenty.