The slope of the line of depreciation is 2,000 (2,000= 24,000/12) if the car's value starts at $24,000. The linear depreciation line formula is y=mx+r where y is the depreciation value, m is the depreciation line slope-intercept, x is the depreciation period, and r is the residual value of the fixed asset. The fixed asset on the problem above has no residual value, therefore r=0.