Which of these graphs represents a function?

Achemist has 200 ml of a 10% sucrose solution. she adds x ml of a 40% sucrose solution. the percent concentration, y, of the final mixture is given by the rational function: the chemist needs the concentration of the final mixture to be 30%. how many milliliters of the 40% solution should she add to the 10% solution to get this concentration?

Solve x+3y=6 and 4x-6y=6 by elimination . show work !

What does independent variable and dependent variable mean in math?