What is the pre image of the vertex a’ if that rule that created the image is r y-axis(x-y) —> (-x, y)?

Taking algebra two apex courses and need with these questions

The verbal translation for the difference of m and 7 increased by 15

Aplane intersects a pris paralel to the base of the prism. the cross section is a polygon wth eight sides. how many sides does the base of the prism have? a. 10 b. 8 c. 7 d. 9