Question 148803
Let x=amount of $0.90 seeds needed; $0.90x=value of these seeds
Then 100-x=amount of $1.30 seeds needed; $1.30(100-x)= value of these seeds
And $1.00(100) equals value of final mixture

Now we know that the value of the seeds before the mixture takes place has to equal the value of the seeds after they are mixed together.  So, our equation to solve is:

$0.90x+$1.30(100-x)=$1.00*100 get rid of parens (distributive law)
$0.90x+$130-$1.30x=$100  subtract $130 from each side

$0.90x+$130-$130-$1.30x=$100-$130  collect like terms
-$0.40x=-$30  divide each side by -$0.40
x=75 kilo-------------------------------------amount of $0.90 seeds needed

100-x=100-75=25 kilo  ------------------------amount of $1.30 seeds needed

CK
75*$0.90+25*$1.30=100*$1.00
$67.5+$32.5=$100
$100=$100

Hope this helps---ptaylor