Answer:
9 liters
Explanation:
it is really easy, you have Ryan's liters + Noel liters = 15 liters
so, the same:
x + y = 15
y = 15 - x
and you need the value of "x"
in the formula C1*V1 + C1*V2 = Cf*Vf
it is:
10%*X + 35%*Y = 20%*15
and we use the value of Y:
0.1*X + 0.35*(15 - X) = 0.2*15
so
0.1*X + 5.25 - 0.35X = 3
0.1X - 0.35X = 3 - 5.25
-0.25X = -2.25
X = 2.25/0.25
X= 9!!!!
:D