“…This paper deals with solvability of functional equations and system of functional equations arising in dynamic programming of multistage decision processes as follows: studied by Bellman [3,4], Bellman and Lee [5], Bellman and Roosta [6], Bhakta and Choudhury [7], Bhakta and Mitra [8], Liu [12], Liu and Ume [13], and others [1,2], respectively; the systems of functional equations f (x) = sup y∈D {u(x, y) + G(x, y, g(a(x, y)))}, ∀x ∈ S, g(x) = sup y∈D {u(x, y) + F (x, y, f (a(x, y)))}, ∀x ∈ S, (1.11) f (x) = inf y∈D {v(x, y) + G(x, y, g(a(x, y)))}, ∀x ∈ S, g(x) = sup y∈D {u(x, y) + F (x, y, f (b(x, y)))}, ∀x ∈ S, (1.12) investigated by Chang [10], Chang and Ma [11], and Liu [12], respectively. By using fixed point theorems, we establish the existence and uniqueness of solutions and iterative approximation for the functional equations (1.1) and (1.2).…”