Please help me to solve this :

4/(x-4)+9/(3x-12)=18

There a total of 82 students in the robotics club and the science club. the science club has 6 fewer students than the robotic club. how many students are in science club?

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?

Mr.walker is looking at the fundraiser totals for the last five years , how does the mean of the totals compare to the median?