Answer
Please see the work below.
Work Step by Step
We can find the mass of Al as
$15.00g\space Cr_2O_3\times \frac{1 mol\space Cr_2O_3}{15.2g\space Cr_2O_3}\times \frac{2mol \space Al}{1 mol \space Cr_2O_3}\times \frac{26.8g\space Al}{1 mol\space Al}=5.3250g\space Al$