Brian, zack, dan, jay, ed, and andrew want to play a two-player video game. if only two people can pay at a time, how many different pairs can they form for the first matchup?
a 12
b 36
c 15
d 30

Brian x Zack
Brain x Dan
Brian x Jay
Brian x Ed
Brian x Andrew
Zack x Dan
Zack x Jay
Zack x Ed
Zack x Andrew
Dan x Jay
Dan x Ed
Dan x Andrew
Jay x Ed
Jay x Andrew
Ed x Andrew

Those are all the possibilities. There are 15, so C would be the correct answer.

Answercounterclockwise rotation about the origin by 180 degrees followed by reflection about the y-axisexplanationthe given figure has verticesrecall that for counterclockwise rotation about the origin, when we rotate figure pqrs counterclockwise through an angle of 180° about the origin, the coordinates will becomenext, we reflect in the y-axis by negating the x-coordinates of the resulting figure to obtain,therefore the correct answer is c