a phone company charges for service according to the formula: C(n)=25+0.02n, where n is the number of minutes talked and C(n) is the monthly charge, in dollars what is the slope?

Can someone me out here number 4 plz

I'm confused on this could anyone me and show me what i need to do to solve it.

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.