what this the font?..help me please!!!!

Arial Bold  Suggeriti da jerseygirl 


Helvetica  Suggeriti da donshottype 
Akzidenz-Grotesk  Suggeriti da donshottype 

IAEA now uses Helvetica Neue for subheadings. See for example IAEA annual report which has embedded fonts https://www.iaea.org/publications/reports/annual-report-2014
However, the font shown in the IAEA logo in your image does not match Helvetica Neue http://www.myfonts.com/fonts/linotype/neue-helvetica/ or the older version of Helvetica.
Don

donshottype - ur fast

Perhaps a variation of Akzidenz-Grotesk Medium. The digital versions such as http://www.myfonts.com/fonts/berthold/akzidenz-grotesk-bq/ do not match exactly
Don