Amechanic charged a customer seperatly for parts and labor the charges for the labor was 15% of the total cost if the charge for the labor was $45 what was the charge for the parts

There are numerous details of immense importance already given in the question. It is important to look at them carefully. Based on those details the answer to the question can be easily determined.
Let us assume the total charges that need to be paid by the customer = x dollars
Percentage of labor cost charged by the mechanic = 15%
Amount of labor cost charged by the mechanic = $45
Then
(15/100) * x = 45
3x/20 = 45
3x = 45 * 20
3x = 900
x = 900/3
   = 300 dollars
Then
The charge that the mechanic charged for the parts = (300 - 45) dollars
                                                                                     = 255 dollars
So the mechanic charged an amount of $255 as the charge of the parts. I hope the procedure is clear for you to understand.

The first one minimumi hope my answer you.

Abit confused about what you mean, but i think you might be referring to slope intercept form: y = mx + bin that case b, or the y intercept is already given.(0,-1)find the slope by using the formulay2 - y1/x2 - x1the final slope will be 4/2, equivalent to 2.now your equation should look like thisy = 4/2x -1sorry if this didn’t you out!