find the slope of the line using two points on the graph, and then you can get your equation in point-slope form. if you need it in slope-intercept form, you can re-arrange your point-slope form equation.
To calculate a circle's area, the formula is Pi R Squared. R is radius. Radius squared would be 36. (6*6) Now, multiplied by Pi, the area would be: 113.04. (36*3.14)