Charlie's weight is nine kilograms greater than his brother's. together they weigh 99 kilograms. let x represent the weight of the little brother. which equation can be used to determine what each one weighs?
a) x2 + 9 = 99
b) 2x - 9 = 99
c) 2x + 9 = 99
d) 3x - 9 = 99

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.