I am getting this error ORA-00907: missing right parenthesis
The foreign key expression is redundant (read: wrong). The syntax is just to add references:
create table passenger(pnr number(10) primary key,trainnumber number(5) references train(trainnumber), -- herenoofseats number(4),price number(4),doj varchar2(10))
change yout CREATE TABLE statement to be like below
create table passenger(pnr number(10) primary key,trainnumber number(5), noofseats number(4),price number(4),doj varchar2(10),foreign key (trainnumber) references train(trainnumber))