10 points and brainlist answer to first correct answer

Aresearch company wants to test the claim that a new multivitamin to improve short term memory. state the objective of the experiment, suggest a population, determine the experimental and control groups, and describe a sample procedure.

You are at a restaurant and owe $38 for your meal. you want to leave a 20% tip. how much will your tip be?

X/y + 4y/x divided by x/y - 2y/x explain as in depth as you can how you simplfied the fractions. i don't know where to start on this : /