First, we have to find slope. We do that by using slope formula. Once we have found slope, we have start to write our equation in slope-intercept form. To get the complete equation, we need to find the y-intercept. To do so, we simply plug in one of the coordinates given to us into our half-formed equation. We should be able to find the y-intercept and then have our complete linear equation once we write it all out.
The probability of picking a blue envelope is 2/8 = 1/4. You want to select a blue envelope twice with replacement so we multiply 1/4*1/4 which is 1/16.