Question 343289
Let A be the amount of 70% antinfreeze, B the amount of 40% antifreeze.
1.{{{A+B=60}}}
.
.
.
{{{70A+40B=52(60)}}}
2.{{{7A+4B=312}}}
From eq. 1,
{{{A=60-B}}}
Substitute into eq. 2,
{{{7(60-B)+4B=312}}}
{{{420-7B+4B=312}}}
{{{-3B=-108}}}
{{{highlight(B=36)}}}gallons
Then from eq. 1,
{{{A+36=60}}}
{{{highlight(A=24)}}}gallons