We assume the cost is proportional to the amount of cheese purchased.
[tex]\dfrac{\$13.45}{5\,\text{pounds}}=\dfrac{\text{cost}}{2\,\text{pounds}}\\\\\text{cost}=(2\,\text{pounds})\times\dfrac{\$13.45}{5\,\text{pounds}}=\$13.45\times\dfrac{2}{5}=\$5.38[/tex]
It would cost $5.38 to buy 2 pounds of cheese.