What is 15 times 15 because i do not know

Which set of reflections would carry trapezoid abcd onto itself? a) x-axis, y=x, y-axis, x-axis b) x-axis, y-axis, x-axis c) y=x, x-axis, x-axis d) y-axis, x-axis, y-axis, x-axis

Can someone me with this problem i don't understand i need

In the polynomial below, what number should replace the question mark to produce a difference of squares? x2 + ? x - 36