Question 328754
Let A be the amount of 25% alcohol, B 35% alcohol.
1.{{{A+B=10}}}
.
.
{{{25A+35B=32(10)}}}
{{{25A+35B=320}}}
2.{{{5A+7B=64}}}
Multiply eq. 1 by (-5) and add to eq. 2,
{{{-5A-5B+5A+7B=-50+64}}}
{{{2B=14}}}
{{{B=7}}}
Then from eq. 1,
{{{A+7=10}}}
{{{A=3}}}
You need to mix 3 gallons of 25% alcohol and 7 gallons of 35% alcohol.