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 $220$ minutes on the phone, and paid ${\$21.50}$. In another month, you spent $380$ minutes on the phone, and paid ${\$25.50}$. 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.

1. This linear model’s slope-intercept equation is .
2. If you spent $200$ minutes over the phone in a month, you would pay .
3. If in a month, you paid ${\$27.50}$ of cell phone bill, you must have spent minutes on the phone in that month.