Name the subsets of the real numbers to which each number belongs 12/18

Express the following as a function of a single angle, cos(60) cos(-20) - sin(60) sin(-20)

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.

The points (1, 7) and (0, 2) fall on a particular line. what is its equation in slope-intercept form?