A bag contains blue marbles and red marbles, 31 in total. The number of blue marbles is 9 less than 3 times the number of red marbles. How many blue marbles are there?

Find the equation of the ellipse with the following properties. the ellipse with foci at (0, 6) and (0, -6); y-intercepts (0, 8) and (0, -8).edit: the answer is x^2 over 28 + y^2 over 64 = 1

Alistair has 5 half-pounds chocalate bars. it takes 1 1/2 pounds of chocalate, broken into chunks, to make a batch of cookies. how many batches can alistair mke with chocalate he has on his hand?

Dana wants to identify the favorite professional baseball team of people in her community. she stands outside a local sporting goods store and asks every other person who enters, "what is your favorite professional baseball team? " will the results of her survey be valid? explain.