How many different ways can a chairperson and an assistant chairperson be selected for a research project if there are 7 scientists available? which counting method do you use?

Ineed with number 17 i don’t get it at alll

Prove that the sum of two consecutive exponents of the number 5 is divisible by 30.if two consecutive exponents are 5n and 5n + 1, then their sum can be written as 30.

Arandom sample of 150 high school students were asked whether they have a job. the results are shown in the table. have a job do not have a job male 48 35 female 41 26 select a ord or phrase from the drop-down menus to correctly complete the statements describing the association.