How do you do numerical integration of a system of ordinary differential equations?

Question

For example

dx = y - a*x^3 + b*x^2 - z + I
dy = c - d*x^2 - y
dz = e*(s*(x-x0) - z)

with
a  = 1
b  = 2.7
c  = 1
d  = 5
s  = 4
x0= -1.6
e = 0.01
I  = 4