Question 27066
The best way to solve these 2x2 linear systems is to first write them in the following form:

Ax + By = C
Dx + Ey = F

And then use the general formula (which you'll find below) to find the solution. We have:

{{{2y+x=4}}}
which is the same as {{{1x + 2y = 4}}}

We also have
{{{4y = x - 1}}}

which is the same as:

{{{1x - 4y = 1}}}

So we have the system:

{{{1x + 2y = 4}}}
{{{1x - 4y = 1}}}

*[invoke linear "x", "y", 1, 2, 4, 1, -4, 1]