What is ratio 120 3:9

The sum of two numbers is 86, and their difference is 20. find the two numbers

The administrator of a large assisted living facility wanted to know the average age of the residents living at the facility. he randomly selected 12 residents and determined their age, listed here: 80, 65, 75, 83, 68, 73, 88, 79, 94, 72, 79, 68 what's the average age of the sample of residents? a. 79 years old b. 68 years old c. 75 years old d. 77 years old

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 : /