As it stands, it is greyed out and says
Result: (no solutions exist)
that's because you typed 5x without white space inbetween 5 and x and also because considering it as linear equation system it is not regular
In[2]:= LinearSolve[{{-5, 1}, {-5, 1}}, {10, 2}]
During evaluation of In[2]:= LinearSolve::nosol: Linear equation encountered that has no solution. >>
Out[2]= LinearSolve[{{-5, 1}, {-5, 1}}, {10, 2}]
Doing
it works, by the way solving the system {y ==5 x + 10 y, y = 5 x + 2}.
