80,531 to the nearest thousand

Which shows the image of rectangle abcd after the rotation (x, y) → (–y, x)?

Write 17/20 as a decimal and as a percent.

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)