√108/3 simplify the expression ASAP plz, I tried by myself and to check it, when i put the equation in, i get different answers

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.