I want to know if what I did is correct.
The problem is:
"A mixture A has a 2% hydrogen solution and a mixture B has a 1.5% of this same solution. How much Mix B must be added to 6 ounces of Mix A in order to get a value of 0.51?"
$$0.02(6)+0.015B=0.51$$ $$0.12+0.015B=0.51$$ $$0.015B=0.51-0.12$$ $$0.015B=0.39$$ $$\frac{0.015B}{0.015}=\frac{0.39}{0.015}$$ $$B=26$$
Therefore, 26 ounces of mixture B must be added to obtain 0.51 of hydrogen.
Yes, that is correct.
Alternatively, we can approach the problem like this. First factor out a $0.005$:
$$0.005(4 \cdot 6 + 3B) = 0.51$$ $$0.005\cdot 3(4 \cdot 2 + B) = 0.51$$ $$\frac{0.005\cdot3(8 + B)}{0.005\cdot3} = \frac{0.51}{0.005 \cdot 34}$$ $$8 +B = 34$$ $$B = 26$$
which is the same process, but using the integers, which makes it much easier.