The average of three numbers is x. if the first number is y and the second number is z, what is the third number?
a) (1/3)x-y-z
b) 3x-y-z
c) x-3y-3z
d)x+y+z over 3

When george started his current job, his employer told him that at the end of the first year, he would receive two vacation days. after each year worked, his number of vacation days will double up to five work weeks (25days) of payed vacation. how many vacation days will he have in 4 years