Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| District | Incumbent | Party | First elected | Result | Candidates |
| --- | --- | --- | --- | --- | --- |
| Pennsylvania 6 | Gus Yatron | Democratic | 1968.0 | Re-elected | Gus Yatron (D) 69.1% Norm Bertasavage (R) 30.9% |
| Pennsylvania 7 | Robert W. Edgar | Democratic | 1974.0 | Retired to run for U. S. Senate Republican gain | Curt Weldon (R) 61.3% Bill Spingler (D) 38.7% |
| Pennsylvania 9 | Bud Shuster | Republican | 1972.0 | Re-elected | Bud Shuster (R) Unopposed |
| Pennsylvania 12 | John Murtha | Democratic | 1974.0 | Re-elected | John Murtha (D) 67.4% Kathy Holtzman (R) 32.6% |
| Pennsylvania 15 | Donald L. Ritter | Republican | 1978.0 | Re-elected | Donald L. Ritter (R) 56.8% Joe Simonetta (D) 43.2% |
| Pennsylvania 17 | George Gekas | Republican | 1982.0 | Re-elected | George Gekas (R) 73.6% Michael S. Ogden (D) 26.4% |
| Pennsylvania 18 | Doug Walgren | Democratic | 1976.0 | Re-elected | Doug Walgren (D) 63.0% Ernie Buckman (R) 37.0% |
| Pennsylvania 21 | Tom Ridge | Republican | 1982.0 | Re-elected | Tom Ridge (R) 80.9% Joylyn Blackwell (D) 19.1% |
Question:
what's the district with first elected being 1972
Answer:
Pennsylvania 9