What are the coordinates of the point (-1.5,9) when reflected across the x-axis?

There are a total of 75 students in the robotics club and science club. the science club has 9 more students than the robotics club. how many students are in the science club?

The number of students who ride a school bus is 110% of the number of students who walk. how many students ride the school bus?

Random variables x poisson~ ( a) ,y poisson ~ ( a) . x and y are independent. if 2 1, 2 1. u =2x+ y-1, v=2x- y +1. find: ) cov (u ,v ).