Slope is the x, since slope is equal to -1, x=-1. For the y intercept you simply add or subtract the number given to you, since it is -5 you would add a -5 to the end of the equation
If we had a sale price of 30% off of $1,050then the sale price is 70% of $1,050 or 0.7(1050) Then we add 7% sales tax to that making thefinal price paid 107% of [0.7(1050)] ... 1.07[0.7(1050)] = $786.45