3x + 2y = -10
5x + y = 9

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)

The diameter of the moon is about 3500 km. approximate the surface area of the moon using the formula for the surface area of a sphere, s = 4? r^2. write your answer in scientific notation.

(25 ! ) what does it mean for an equation to have no solution or infinitely many solutions?