Question 343306
Let A be the amount of 60% acid solution, B the amount of 75% acid solution.

1.{{{A+B=20}}}
.
.
.
{{{60A+75B=72(20)}}}
{{{60A+75B= 1440}}}
2.{{{4A+5B=96}}}
From eq. 1, 
{{{A=20-B}}}
Substitute into eq. 2,
{{{4(20-B)+5B=96}}}
{{{80-4B+5B=96}}}
{{{highlight(B=16)}}}liters
Then from eq. 1,
{{{A+16=20}}}
{{{highlight(A=4)}}}liters