To plan its upcoming programming, a local television station wanted to study the television watching habits of people in the area. Station executives called a random sample of people in their broadcast area and asked them a variety of questions. In particular, they asked people their ages, x, and how many hours of television they had watched last week, y. Find the equation for the linear regression model that fits the data.

A medical student reads that with enough sun exposure, the human body can manufacture vitamin D3. This sounds too amazing to be true, so he decides to test it out. Over the next few weeks, he spends a varying number of hours in the sun, x. At the end of each week, he measures the concentration of vitamin D3 in his blood (in nanograms per milliliter), y. Find the equation for the linear regression model that fits the data.