let say if i want to plot J[n], S[n], A[n] on the x,y plane then should i use Array to store all the value?

J_(n)=0.5*A_(n)        

S_(n+1)=0.75*J_(n)

A_(n+1)=0.8*S_(n)+0.7*A_(n)

initial condition : A₀=70 , J₀=75 , S₀=80

myDE:=proc(n)

local i, A,J,S;

A₀:=70;

S₀:=80;

J₀:=75;

for i from 1 to n do

i don't think this is right.