Three vouchers are: 3*50= 150, which exceeds the total consumption, so only two vouchers can be used at most.

2 vouchers, which can be deducted: 25*2=50 yuan,

So the best we can do is give 50 yuan a discount.

2. If you spend X yuan, you need to pay:

50+(x-50)*0.6=0.6x+20

Payment is required to use vouchers:

x-25 x & lt； 100

x-50？ 100 & lt； x & lt 150

x-75x & gt； 150

According to the meaning of the question:

When 0.6x+20+ 15 = x-25x

X= 150, give up if you are not satisfied.

When 0.6x+20+ 15 = x-50x

X=2 12.5, if you are not satisfied, give up.

When 0.6x+20+ 15 = x-75x >; 150

X=275, which satisfies the meaning of the question.

So, they spent 275 yuan

You need to pay: 0.6*275+20= 185 yuan.