Which one..? need help. :)

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

There are 8 movies that you would like to see currently showing in theatres. in how many different ways can you choose a movie to see this saturday and one to see this sunday?

Isabelle is mixing red and blue paint to make purple paint she adds 3/10 of a fluid ounce of red to 12/25 of a fluid ounce of blue to make 1 1/30 fluid ounces of purple how many fluid ounces of red paint ounces of red paint will she need to make 3 fluid ounces of purple paint