answer is C.
from the question
let m be Mary's annual salary, j Jim's and k Kate's.
m-j=2(m-k)
m>j and m>k
from 1) j=30k, can't figure out m or k, insufficient
from 2)k=40k, can't figure out m or j, insufficient
together
we know that m>k>j
m-30=2(m-40)
m-30=2m-80
m=50
so the mean is 50+40+30/3 = 120/3 = 40, sufficient.
P.S. - you don't have to actually calculate the result, only understand that from 1 and 2 you can get m and that makes it sufficient.
from the question
let m be Mary's annual salary, j Jim's and k Kate's.
m-j=2(m-k)
m>j and m>k
from 1) j=30k, can't figure out m or k, insufficient
from 2)k=40k, can't figure out m or j, insufficient
together
we know that m>k>j
m-30=2(m-40)
m-30=2m-80
m=50
so the mean is 50+40+30/3 = 120/3 = 40, sufficient.
P.S. - you don't have to actually calculate the result, only understand that from 1 and 2 you can get m and that makes it sufficient.
