Solve the system using substitution. y= -6x+54 5y-x+9=0

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?

What is the radius of a circle with an area of 78.5 cubic inches? use 3.14 for pie

3x + 4y = 5 x- 3y = -7 solve by substitution