First you should write those results as "Ax= ", "Ay= ", and "Az= ", not "x= ", etc.
The columns of A are, of course, , , and
You want to write [tex]Ax=
so you need to solve the three equations , , and for , , and .
For the second problem, you are simply being asked to multiply two matrices. Don't you know how to do that? You seem to have multiplied a matrix and a vector (column matrix). Just multiply the first matrix times each column in the second matrix, giving the three columns of the product matrix.