Answer
The atomic weight of chromium is equal to $51.9959amu$.
Work Step by Step
Considering the natural abundance of chromium isotopes, we can obtain its atomic weight by following:
$Ar(Cr)=0.0435\times49.9461amu+0.8379\times51.9405amu+0.0950\times52.9406amu+0.0236\times53.9389amu=51.9959amu$
We need to multiple the natural abundance of each of the chromium isotopes by its mass and then calculate the sum of those products in order to obtain the atomic weight of chromium.