What properties were use commutative or associative or both (9+k)+10=(9+10)+k

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.

10 ! in a race, nick is 50 feet in front of jay after ten seconds. how fast can nick run, if jay can run 20 feet per second?

15/16 as a decimal rounded to the nearest hundredth