Hello, you can help me ? in this exersice

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?

Given that ot =5, xt=12, and ox= 13 is xy tangent to circle o at t? explain.

Can anyone explain to me how to do this? anything will .