What is the answer to Rx+12r+8r

Of the ones listed here, the factor that had the greatest impact on the eventual destruction of native americans' ways of life was the development of the a) automobile. b) highway. c) railroad. d) steamboat.

Askyscraper is 396 meters tall. at a certain time of day, it casts a shadow that is 332 meters long.at what angle is the sun above the horizon at that time?

Aladder that is 20ft long is leaning against the side of a building. if the angle formed between the ladder and the ground is 75 degrees how far is the bottom of the from the base of the building?