Ring the number that is 10 more than 36

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?

Ijust need to see how to do this. so you don’t have to answer all of them just a step by step explanation of one.

If f(x) = x+8 and g(x) = 4x- 3, find (f+g)(x)