If x = 30 degree, then which expression is equivalent to 1/2?
a. -sin x
b. sin x
c. -cot x
d. cot x

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.