If I have interpreted the question correctly, the solution is as follows:
Now, I run into a problem, but first let me explain to you what I've done. Each of the four columns (not including the constant column) corresponds to x1,x2,x3, and x4. The first column is x1, the second column is x2, the third column is x3, and the fourth column is x4. Look at the first row (That is the first equation). The first number in the first row is 1, and since this is in column one, we multiply this by x1. Now we add to that: the second number in the first row is 1/2 ,and since this is in the second column we multiply that by x2. We continue similarly all through the matrix.
The problem I encountered was in the last row. The fourth element should not be zero. In this case, only the first three elements of the last row should be zero.With the numbers you've given, we have 0+0+0+0=1 and this is obviously wrong. Have you made a typo?