Answer :
Let x cubic cm of 10% acid is mixed with (150-x) cubic cm of 4% solution to obtain 150 cubic cm that is 6% acid .
Therefore the equation is
[tex]0.1x + 0.04(150-x) = 0.06*150 \\ 0.1x + 6 -0.04x = 9[/tex]
Combining like terms, we will get
[tex]0.06x = 3[/tex]
Dividing both sides by 0.06,
[tex]x = \frac{3}{0.06} \\ x = 50 \ cubic \ cm[/tex]
50 cubic cm of 10% acid is mixed with
[tex](150-50)=100 \ cubic \ cm[/tex]
of 4% solution to obtain 150 cubic cm that is 6% acid .