If I use a predetermined overhead rate based on dirct labor hours to apply manfacturing overhead to jobs. My estimated manfacturing overs cost was $300,000 based on an estimated activity level of 100,000 direct labor our. Actual overhead amounted to $325,000 with actual direct labor hours totaling 110,000 for the month. How much was the overapplied or underapplied overhead

You need a rate first which is:

\text\frac{estimated total overhead costs}{estimated activity base}

Once you have that rate, it's used to apply the overhead. You apply it based on the actual level of the activity base. Then you can compare the applied overhead calculated to the actual overhead costs given.