Erica has $12 credit on her Cel-Tel phone card. It costs her $1 to make a phone call using her Cel-Tel card. Erica also has $15 credit on her MTT phone card. It costs her $2 to make a phone call using her MTT card. Which system of equations can be solved to find the number of calls, x, that Erica can make and have the same amount of money, y, on both phone cards? yy==−2x+15−x+12
y = - 2 x + 15 y = - x + 12

yy==2x+15−x+15
y = 2 x + 15 y = - x + 15

yy==−2x−15−x−12
y = - 2 x - 15 y = - x - 12

yy==15x−212x−1
y = 15 x - 2 y = 12 x - 1