Answer
$300$ liters
Work Step by Step
Using the analogy of the formula from Exercise 105, we can come up with our own formula for this problem. $74\%$ or $0.74$ is given as the value for $C$, or the new concentration when $x$ liters of pure acid are added to $200$ liters of a $35\%$ solution.
We plug in the new $C$ to the formula, and we distribute and combine like terms, isolating the $x$-term and then dividing to solve for $x$.
$C=\frac{x+0.35(200)}{x+200}$
$0.74=\frac{x+0.35(200)}{x+200}$
$0.74(x+200)=x+70$
$0.74x+148=x+70$
$.26x=78$
$x=\frac{78}{.26}$
$x=300$
