Question 906495
a+b=1,
0.07*a+0.28*b=0.196*1
a=1-b
0.07*(1-b)+0.28*b=0.196
0.07-0.07b+0.28*b=0.196
0.21*b=0.126
b=0.6
a=1-b
a=0.4  liter at 7% 400 mL
b=0.6  liter at 28% 600 mL
check
0.07*0.4+0.28*0.6=0.196*1
0.028+0.168=0.196
0.196=0.196
ok