What is the atomic mass of iridium?

Iridium has two isotopes. Iridium-191 has a mass of 191.0 amu and a percent abundance of 37.58%. Iridium-193 has a mass of 193.0 amu and a percent abundance of 62.42%.

$\text{Atomic mass of Ir"-={37.58%xx(191)+62.42%xx(193)}*"amu}$
$= 192.25 \cdot \text{amu}$.