Question 1142452
x = amount of 30% solution.
y = amount of 45% solution.


x + y = 30
.3 * x + .45 * y = .39 * 30


in the first equation, solve for y to get y = 30 - x.


in the second euation, replace y with 30 - x to get .3 * x + .45 * (30 - x) = .39 * 30.


simplify to get .3 * x + 13.5 - .45 * x = 11.7.


combine like terms and subtract 13.5 from both sides of the equation to get -.15 * x = -1.8


solve for x to get x = -1.8 / -.15 = 12


y = 30 - x = 30 - 12 = 18.


you have x = 12 and y = 18.


x + y = 30
.3 * x + .45 * y = .3 * 12 + .45 * 18 = 3.6 + 8.1 = 11.7.
11.7 / 30 = .39


solution looks good.


solution is 12 cc of 30% solution and 18 cc of 45% solution are combined to make 30 cc of 39% solution.