Date: Jan 29, 2013 11:24 AM
Author: Phil Goddard
Subject: Re: how to implement coupled ordinary differential equation in Simulink ?

Get 3 continuous time integrators; label their inputs y1dot, y2dot and y3dot; label their outputs y1, y2, y3.
Get appropriate blocks from the Math library (sum, product, math fcn, etc).

Form the right hand side of your equations; feed the result into the inputs of the integrators.