Question 485902
Let she will add x ml of 9% solution, then she will receive (80+x) ml of 7 % solution
{{{80*0.02+x*0.09=(80+x)*0.07}}}
{{{1.6+0.09x=5.6+0.07x}}}
{{{0.09x-0.07x=5.6-1.6}}}
{{{0.02x=4}}}
{{{x=4/0.02}}}
{{{x=200}}}ml of 9% solution