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\begin{document}$${\mathcal {F}}$$\end{document} of r-graphs, the Turán number of F\documentclass[12pt]{minimal}
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\begin{document}$${\mathcal {F}}$$\end{document} for a given positive integer N, denoted by ex(N,F)\documentclass[12pt]{minimal}
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\begin{document}$$ex(N,{\mathcal {F}})$$\end{document}, is the maximum number of edges of an r-graph on N vertices that does not contain any member of F\documentclass[12pt]{minimal}
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\begin{document}$${\mathcal {F}}$$\end{document} as a subgraph. For given r≥3\documentclass[12pt]{minimal}
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\begin{document}$$r\ge 3$$\end{document}, a complete r-uniform Berge-hypergraph, denoted by Kn(r)\documentclass[12pt]{minimal}
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\begin{document}$${K}_n^{(r)}$$\end{document}, is an r-uniform hypergraph of order n with the core sequence v1,v2,…,vn\documentclass[12pt]{minimal}
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\begin{document}$$v_{1}, v_{2}, \ldots ,v_{n}$$\end{document} as the vertices and distinct edges eij,\documentclass[12pt]{minimal}
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\begin{document}$$e_{ij},$$\end{document}1≤i<j≤n,\documentclass[12pt]{minimal}
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\begin{document}$$1\le i<j\le n,$$\end{document} where every eij\documentclass[12pt]{minimal}
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\begin{document}$$e_{ij}$$\end{document} contains both vi\documentclass[12pt]{minimal}
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\begin{document}$$v_{i}$$\end{document} and vj\documentclass[12pt]{minimal}
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\begin{document}$$v_{j}$$\end{document}. Let Fn(r)\documentclass[12pt]{minimal}
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\begin{document}$${\mathcal {F}}^{(r)}_n$$\end{document} be the family of complete r-uniform Berge-hypergraphs of order n. We determine precisely ex(N,Fn(3))\documentclass[12pt]{minimal}
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\begin{document}$$ex(N,{\mathcal {F}}^{(3)}_{n})$$\end{document} for N≥n≥13\documentclass[12pt]{minimal}
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\begin{document}$$N \ge n \ge 13$$\end{document}. We also find the extremal hypergraphs avoiding Fn(3)\documentclass[12pt]{minimal}
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\begin{document}$${\mathcal {F}}^{(3)}_{n}$$\end{document}.
