It appears that you are using floating-point numbers (d.dd) in your input to Solve. Try NSolve, which is designed to handle floating-point numbers.
Another method is to convert the equations to use only exact numbers.
In[1]:= equ = Rationalize[ 3.4 x^2 + x/2.2 == 0.137, 0]
Out[1]=
2
5 x 17 x 137
--- + ----- == ----
11 5 1000
In[2]:= Solve[ equ, x]
Out[2]=
-250 - Sqrt[626118] -250 + Sqrt[626118]
{{x -> -------------------}, {x -> -------------------}}
3740 3740
In[3]:= N[%]
Out[3]= {{x -> -0.278416}, {x -> 0.144726}}
My understanding is that 0``-9.295... means you have less than zero significant digits in the output. It may be that 9.0 simply did not check for such things.
