By your cell phone contract, you pay a monthly fee plus some money for each minute you use the phone during the month. In one month, you spent 230 minutes on the phone, and paid $17.45. In another month, you spent 370 minutes on the phone, and paid $19.55. Let x be the number of minutes you talk over the phone in a month, and let y be your cell phone bill for that month. Use a linear equation to model your monthly bill based on the number of minutes you talk over the phone.
a) This linear model’s slope-intercept equation is

b) If you spent 150 minutes over the phone in a month, you would pay

c) If in a month, you paid $21.50 of cell phone bill, you must have spent
minutes on the phone in that month.