Need to know ASAP!! If you can help

What is x and y (use substitution? ) 5x+3y=38 and y=3x+8?

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?

Complete the solution of the equation. find the value of y when x equals to 1 9x-5y=29