1.Because the variable m does not appear in Ax + By = C, equations in this form make it impossible to determine the line's slope m.This statement does not make sense, so how could I found m and what would it be. Example

2.If I drive x miles in a year, the formula C = 0.25x +3,500 models the annual cost, C, in dollars, of operating my car, so the equation shows that (a) with no driving at all, the cost is $3,500, and (b) the rate of increase in the cost is $0.25 for each mile I drive.I need help with a and b.