Andrew and maria each collected six rocks, and the masses of the rocks are shown in the table above. the mean of the masses of the rocks maria collected is 0.1 kilogram greater than the mean of the masses of the rocks andrew collected. what is the value of x ?

Since no table is provided, so I'll just tell you how to answer this problem and you can apply using the numbers in the table.
I'll assume that x is a missing mass of one of Andrew's rocks.

Masses of the rocks that maria collected: m1, m2, m3, m4, m5 and m6
Masses of the rocks that andrew collected: n1, n2, n3, n4, n5 and x
where m1, m2, m3, m4, m5, m6, n1, n2, n3, n4 and n5 are masses recorded in the table.

Mean of mass of maria's rocks = (m1+m2+m3+m4+m5+m6) / 6 = y Kg
Mean of mass of andrew's rocks = (n1+n2+n3+n4+n5+x)/6 = z

It is given that: y = z+0.1
If you substitute in the above two equations, the only unknown will be x. It can be easily calculated then.

Ithink the answer would be a