Rodger can do 46 pushups.
50 * 0.92 = 46
Edit: To better clarify, 0.92 is from 1.00 - 0.08.
... 8 percent fewer than 100 percent is 92 percent; 1.00 - 0.08 = 0.92
Keep in mind that:
1.00 = 100%
0.08 = 8%
0.92 = 92%
After finding this you may multiply 50 * 0.92 to get 46.