I can't figure out the answer

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15

Asequence is defined recursively using the formula f(n + 1) =f(n) - 5. which sequence could be

Abag contains 3 red marbles, 2 blue marbles, and 2 green marbles. one marble is picked, then another marble. assume that the selections are made with replacement. a) find the probability of picking two red marbles with replacement. b) find the probability of picking a red marble and a blue marble. assume the selections are made without replacement. c) find the probability of picking two red marbles without replacement. d) find the probability of picking a red marble and a blue marble without replacement.