  This paper addresses the qualitative theory of mixed-order positive linear
coupled systems with bounded or unbounded delays. First, we introduce a general
result on the existence and uniqueness of solutions to mixed-order linear
coupled systems with time-varying delays. Next, we obtain the necessary and
sufficient criteria which characterize the positivity of a mixed-order delay
linear coupled system. Our main contribution is in Section 5. More precisely,
by using a smoothness property of solutions to fractional differential
equations and developing a new appropriated comparison principle for solutions
to mixed-order delayed positive systems, we prove the attractivity of
mixed-order non-homogeneous linear positive coupled systems with bounded or
unbounded delays. We also establish a necessary and sufficient condition to
characterize the stability of homogeneous systems. As a consequence of these
results, we show the smallest asymptotic bound of solutions to mixed-order
delay non-homogeneous linear positive coupled systems where disturbances are
continuous and bounded. Finally, we provide numerical simulations to illustrate
the proposed theoretical results.
