can someone help my friend with math?

Question

A pharmacist wishes to make 1.8 L of a 10% solution of boric acid by mixing 7.5% and 12% solutions. How much of each type of solution should be used?

Answer 1

x volume of 7.5%
y volume of 12%

Volume balance
x + y = 1.8
y = 1.8 - x

Mass balance
1.8*0.1 = x*0.075 + y*0.12

Put y=1.8 - x in this equation. Solve for x and then find y.

Answer 2

CV=C1V1 + C2V2
CV= C1(1.8-V2) + C2V2
CV=1.8C1-C1V2 + C2V2
CV-1.8C1= (-C1+C2)V2
V2=(CV-1.8C1)/(-C1+C2)
=(10*1.8L-(1.8*7.5))/(-7.5+12)
V2=1L
V1=1.8L-1L=.8L

Answer 3

i have no freaking clue what you just asked me dude