distribute a amount of dollars which is 500 among both of the 2 brothers combined and 1 sister the sister gets twice as much of the brothers find how much the brothers got and the sister

Lizette is training for a marathon. at 7: 00 she left her house and ran until 8: 30, then she walked until 11: 30. she covered a total distance of 18 miles. her running speed was six miles per hour faster than her walking speed. find her running and walking speeds in miles per hour.