im afraid you have to use the quadratic formula for this problem, -b +/1 squareroot (b^2-4ac)/2a
a= 3 b=3 c= -5
-3 +/- squareroot (-51)/6 (negative squareroots mean you have to use imaginary numbers )
if my work is right
x= -0.5 +1.19023i
x= -0.5- 1.19023i
hope this helped