According to the meaning of the question:
2.5X + 1.5Y =30.5... 1
2X + 3Y =46...2
1 type +2 type
4.5X + 4.5Y = 76.5
So X+Y = 17.
So 1.5X+ 1.5Y = 25.5.
So I overcharged 0.5 yuan.