What is the equation of the line that passes through piont (6,18) and has a y-intercept of -2

You have essentially been given 2 points to work with: (6,18) and (0,-2). If you are getting the point-slope form equation, here's what you would do:

There's a formula for finding the slope of a line: (y2-y1) / (x2-x1). In this case, the equation would be (-2-18) / (0-6), -20/-6, or 10/3 (essentially 3 1/3). You would then insert the slope into the equation along with your y-intercept, -2, and end up with y=(10/3)x-2.

20 percentage, you can also do it on a calculator.