Question 903516
w chickens
x cows
y horses
z pigs


{{{y/x=4}}};
{{{w/x=12}}};
{{{x+z+y=w}}};
{{{w+x+y+z=54}}}.


Four equations (linear) and four unknown variables.
Which methods do you know?
Which method do you want to use?


The last two equations are interesting.  You should be able to subtract one of them from the other to eliminate some variables to quickly solve for one variable, specifically for w.  Arrange the form of these two equations as:
{{{system(-w+x+y+z=0,w+x+y+z=54)}}}.
...  without showing that work, one may see that {{{highlight(w=27)}}}.
...
Continue using whatever you know how to do.