let peanuts be p
and cashews be c
Since he wants a total of 20 pound, so we can write:
[tex]p+c=20[/tex]Peanut cost 10 and cashews cost 9 (per pound) and total 20 pounds cost 9.70*20 = 194 dollars, thus we can write:
[tex]10p+9c=194[/tex]Rearranging the first equation, we have:
[tex]\begin{gathered} p+c=20 \\ p=20-c \end{gathered}[/tex]Plug this into 2nd equation and solving for c gives us:
[tex]\begin{gathered} 10p+9c=194 \\ 10(20-c)+9c=194 \\ 200-10c+9c=194 \\ 200-194=10c-9c \\ 6=c \end{gathered}[/tex]Since we know p = 20 -c, so
p = 20 - 6 = 14
So, the mixture should be:
14 pounds peanuts, and
6 pounds of cashews