Answer
$40$ pounds of peanuts and $60$ pounds of walnuts.
Work Step by Step
Let $x$ be the amount of peanuts. Then the amount of walnuts is $100-x$. Then our equation is: $1.49x+(100-x)\cdot2.69=100\cdot2.21\\1.49x+269-2.69x=221\\-1.2x=-48\\x=40.$
Thus he mixed $40$ pounds of peanuts and $60$ pounds of walnuts.