Step-by-step explanation:
If x is the volume of pure water:
Initial + added = final
0.95 (840) + 0 (x) = 0.70 (840 + x)
798 = 588 + 0.70 x
x = 300
840 + x = 1140
You need to add 300 mL of pure water to obtain 1140 mL of the desired 70% solution.
You can draw 12 dots plus two other dots because 8 divided by 4 is two