Linear combination of others Write one of the vectors as a linear combination of the others.
$$ \left[
    \begin{array}{cc|c}
      0\\
      1\\
      1
    \end{array}
\right],\left[
    \begin{array}{cc|c}
      1\\
      0\\
      -1
    \end{array}
\right],\left[
    \begin{array}{cc|c}
      4\\
      5\\
      1
    \end{array}
\right] $$ 
So far, this is what I have done:
I took the 3 vectors and made them into a matrix.
$$ \left[
    \begin{array}{ccc}
      0&1&4\\
      1&0&5\\
      1&-1&1
    \end{array}
\right] $$
Then I put it into RREF and got the matrix below.
$$ \left[
    \begin{array}{ccc}
      1&0&5\\
      0&1&4\\
      0&0&0
    \end{array}
\right] $$
I don't know how to continue this problem.

The last column is the coefficients in your linear combination. So 
$$5(0,1,1)+4(1,0,-1)=(4,5,1)$$
