Which number sentence shows the commutative property of addition? a. 8 + 4 = 12 b. 8 + 4 = 4 + 8 c. 8*4 = 32 d. 3 + (9 + 1) = (3 + 9) + 1 asap !

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.