You have 8 names of people on a list. If you randomly chose pairs of two's, how many potential pairs are there?

Icould really use some with this question.

Can someone me with the property questions for 12 13 and 14 plz

Three numbers x, y, and z are in the ratio 2: 7: 8. if 12 is subtracted from y, then three numbers form a geometric sequence (in the order x, y–12, z). find x, y, and z. there are 2 sets.