The mass of $0.25$ moles of silver is: 

$\left[\mathrm{Ag}=108\right]$

The number of atoms in 0.05 g of hydrogen is: 

$\left[\mathrm{H}=1\right]$

The number of atoms in 0.008 g of phosphorus is:

$\left[\mathrm{P}=31\right]$

The number of atoms in $8$ g of iron is:

$\left[\mathrm{Fe}=56\right]$