Assuming you are using SQL Server. There are number of problems in your script.
1) The data type is
numeric(x,y)
not
number(x,y)
2) You can only specify PRIMARY KEY constraint once. Do not use the inline definition if you need compound primary key.
3) Your foreign keys need to specify the target table and column.
4) Use named constraints, it will save you lots of trouble later.
Here is how it should look like:
CREATE TABLE job
(
TaskId char(4) NOT NULL,
EmpId char(2) NOT NULL,
HoursSpent numeric(3,1) NOT NULL CONSTRAINT DF_job_HoursSpent DEFAULT (20.0),
CONSTRAINT PK_job PRIMARY KEY (TaskId, EmpId),
CONSTRAINT FK_job_task FOREIGN KEY (TaskId) REFERENCES task (TaskId),
CONSTRAINT FK_job_empoyee FOREIGN KEY (EmpId) REFERENCES employee (EmpId)
);