M/s, the speed of Party A and Party B is B respectively.

M/s,

Then, (a+b)* 15=255.

(a-b)* 17=255

Solution, a= 16

b= 1

2. We assume that the downhill time is 1 hour, the flat road is b hours, the flat road is c hours, and the uphill is d hours.

Then,

a+b=55/60

c+d= 1.5

12a=4d

9b=8c

Solution, b=2/3

a= 1/4，c=3/4

d=3/4

We assume that before the discount, A sells A yuan and B sells B yuan.

Then 5a+b=84

6a+3b= 108

Solution, a= 16, b=4.

rule

50a+50b= 1000。 After the discount, I spent 960 yuan, so I spent 40 yuan less.

Suppose the total output value last year was 1 million, and the expenditure last year was 2 million.

rule

a-b=200

1.2a-0.9b=780 (There is something wrong with the title. Write today's profit as 780 yuan, and I calculate it according to this year's profit of 7.8 million).

Solution, a=2000, b= 1800.

5. Set tomatoes 1 kg, beans 2 kg,

Then, 1.2a+ 1.6b=60.

a+b=40

Solution, a= 10, b=30.

So he can earn (1.8-1.2) *10+(2.5-1.6) * 30 = 33 after selling.