16. 75/100 whats inside the big 1

Let X = ml's of 3% hydrochloric acid and Y = ml's of 10% hydrochloric acid

Add X and Y to get the total milliliters:

X + Y = 175

Now multiply the quantities by their percentages go get the 6% required:

0.03x + 0.10y = 0.06(175)

Rewrite the first equation as x = 175 -y

Now replace x in the second equation and solve:

0.03(175-y) + 0.10y = 0.06(175)

Simplify:

5.25 - 0.03y + 0.10y = 10.5

Combine like terms:

5.25 +0.07y = 10.5

Subtract 5.25 from both sides:

0.07y = 5.25

Divide both sides by 0.07:

y = 5.25 / 0.07

y = 75

Now you have y solve for x:

x = 175-y = 175 - 75 = 100

You need  100 ml's of the 3% solution and 75 ml's of the 10% solution.