[求助]问一道去年12月的JJ，盼望解答

set X has 5 numbers, and the average is greater than medium; set Y has 7 numbers, and the average is greater than medium. set Z combined x and y, is the average greater than medium?

(1) medium of set X is greater than medium of set Y (2)average of set X is greater than average of set Y

题目意思都懂，就是应该从哪里入手呢？思路？