From (1), the arithmetic mean point of X and 10 sits at the middle of the segment from X to 10.
If Z sits between X and 10 and it is nearer to 10 than to X.
Then it can be concluded that Z>1/2(X+10).
If Z sits right to 10, definitely it is greater than 1/2(x+10).
So (1) alone is sufficient.
From (2), [Z-1/2(x+10)]=[5x-1/2(x+10)]=[(9x-10)/2], the result depends on value of X. So (2) alone is not sufficient.
I think A is correct. |