How to write an equation for a horizontal line going through 4

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?

Planning for the possibility that your home might get struck by lighting and catch on fire is part of a plan for ?

When y’all answer can y’all explain too !