In this paper, we consider the nonlocal elliptic problem involving a mixed local and nonlocal operator, (P){(integral Omega f(x, u)dx)(beta) (sic)(p, s)(u) = f (alpha)(x, u) in Omega, u > 0 in Omega, u = 0 in R-N \Omega, where Omega subset of R-N is a bounded regular domain, (sic)(p, s) equivalent to - Delta p + (-Delta)(p)(s), 0 < s < 1 < p < N, alpha, beta is an element of R and f : Omega x R -> R be a nonnegative function which is defined almost everywhere with respect to the variable x. Using Schauder and Tychonoff fixed point theorems, we get two existence theorems of weak positive solutions under some hypothesis on alpha, beta and f