Explanation:
Warren bought 2 pounds of hazelnuts, which cost $8.04 per pound, so he spent:
2 pounds * $8.04/pound = $16.08
He also bought 1 pound of walnuts, which cost $5.13 per pound, so he spent:
1 pound * $5.13/pound = $5.13
Therefore, the total amount Warren spent is:
$16.08 + $5.13 = $21.21