What does the mode of this set of data represent?

Solve the system of equations. y= 2x y= x^2 - 15

Can someone pls ! pls answer all. no explanation needed..

If the speed of an electromagnetic wave is 100,000 cm/s and its wavelength is 100 cm, what is its frequency? a) 100,000 cycles per second (hz) b) 1 × 10-3 cycles per second (hz) c) 10,000,000 cycles per second (hz) d) 1,000 cycles per second (hz)