#### PROBLEM 824-THE PENTAGON JOURNAL

Proposed by Pedro Pantoja-Brazil SOLUTION 824 Solution by Khanh Hung Vu-Vietnam

#### ELEGANT INEQUALITY-195

Proposed by Daniel Sitaru-Romania ELEGANT INEQUALITY-195 Solution by Khanh Hung Vu-Vietnam

#### ELEGANT INEQUALITY-194

Proposed by Daniel Sitaru-Romania ELEGANT INEQUALITY-194 Solution 1 by Tran Hong-Vietnam, Solution 2 by Khanh Hung Vu-Vietnam

#### ELEGANT INEQUALITY-128

Proposed by Daniel Sitaru-Romania ELEGANT INEQUALITY-128 Solution by Khanh Hung Vu-Ho Chi Minh-Vienam

#### HUNDREDS OF CIRCLES

Proposed by Francisco Javier Garcia Capitan-Spain HUNDREDS OF CIRCLES Solution by Khanh Hung Vu-Ho Chi Minh-Vietnam

#### SYSTEM-19

Proposed by Bogdan Rublyov-Ukraine SYSTEM-19 Solution by Khanh Hung Vu-Ho Chi Minh-Vietnam

#### FUNCTIONAL EQUATION-7

Proposed by Marian Ursarescu-Romania FUNCTIONAL EQUATION-7 Solution by Khanh Hung Vu-Ho Chi Minh-Vietnam

#### SHAN HE WU’S INEQUALITY

Proposed by Shan He Vu-China SHAN HE WU’S INEQUALITY Solution 1 by Khanh Hung Vu-Ho Chi Minh-Vietnam, Solution 2 by…

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#### CONTRAHARMONIC MEAN

Proposed by Abdilkadir Altintas-Afyonkarashisar-Turkey CONTRAHARMONIC MEAN Solution by Khanh Hung Vu-Ho Chi Min-Vietnam

#### GEOMETRIC PROBABILITY-1

Proposed by Daniel Sitaru-Romania GEOMETRIC PROBABILITY-1 Solution by Khanh Hung Vu-Ho Chi Minh-Vietnam