The compressions and rarefraction that make up a sound wave traveling through the air are 1. differences in air pressure.
2. differences in pitch.
3. echoes.
4. an example of infrasound.

Acamper leaves camp on a kayak and travels 50 miles east on a river, then he ties his kayak to the bank and travels 20 miles north on a bicycle. this trip can be plotted on the coordinate plane, where the camp is the point (0, 0). the distant of the camper to the camp can be found using the distance formula. which other formula can he use? a) 502 - 202 b) 502 + 202 c) 502 - 202 d) 502 + 202

7x+8y=-18, 4x-9y=-3 solve the system of equations

How is working backward similar to solving an equation?