5. A science teacher has a supply of 50% sugar solution and a supply of 80% sugar solution. How much of each solution should the teacher mix together to get 105 mL o 60% sugar solution for an experiment? (4 points)
Let x be the amount of the 50% sugar solution in mL.
Then the amount of the 80% sugar solution is 105 - x mL.
The amount of sugar in the 50% solution is 0.5x mL.
The amount of sugar in the 80% solution is 0.8(105 - x) mL.
The total amount of sugar in the mixture is 0.6 * 105 mL.
0.5x + 0.8(105 - x) = 0.6 * 105.
0.5x + 84 - 0.8x = 63.
-0.3x = -21.
x = -21/-0.3 = 70 mL.
The science teacher should mix 70 mL of the 50% sugar solution with 105 - 70 = <<105-70=35>>35 mL of the 80% sugar solution to obtain a 105 mL of the 60% sugar solution. Answer: \boxed{70}.