Find a solution amount- mixture problem

Question

A chemist needs 50 mL of a 16% Salt solution for an experiment. She can can only find a 13% Salt solution and an 18% Salt solution in the supply room. How many milliliters of each should be mixed to produce the desired amount of the 16% solution?

Answer 1

X+Y = 50

0.13X + 0.18Y = 0.16*50 = 8

0.13X + 0.18(50-X) = 8

0.13X + 9 - 0.18X = 8

-0.05X = -1

5x = 100

x=20

20 mL of the 13% salt solution

30 mL of the 18% salt solution