We let the amount of 32% acid solution added to be X ,
Firstly, 40 of 0.12 conc. , = 4.8L of acid, and 35.2L non acid
For ever 1 L of 32% acid we add in we get 0.32L of acid and + 0.68L non Acid,
So we formulate an equation
(4.8+0.32X) / (40+X) = 16/100
(4.8+0.32X) = 0.16(40+X) =6.4+0.16X
0.16X = 1.6
X =10
Hence she used 10L of 32% Solution acid.
Anything inside a square foot can be multiplied together. In this case, it forms :

So, B is the correct answer.
Technically, that expression can be further simplifyed, but that is not required on this question, so you're all good!
The points (-3,0) and (-3, 1). Actualy any point of type (-3, n) where n is ant number