The first one is 5%
Second - 76 is 15 percent of what number? If we substitue "what number" in the question "76 is 15 percent of what number?" with 506.67, we get this sentence: 76 is 15 percent of 506.67. Since this statement is true, we know that our answer is correct.
Third - 25 percent (calculated percentage %) of what number equals 50? Answer: 200.