1) x + y = 5
2) 4x - 2y = 20
3) 4x - 3y =12
4) 6x - y= 18

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.