1 、( 1)x = 3 1/ 12(2)x = 48/55

y= 1 1/4 y=-(28/55)

2. solution: let the average speed of the plane be x km/h and the wind speed be y km/h. according to the meaning of the question, we can get:

( 10/3)(x-y)= 1200

(5/2)(x+y)= 1200

To solve this system of equations, x=420.

y=60

A: The average speed of an airplane is 420 kilometers per hour, and the wind speed is 60 kilometers per hour. ..

3. Solution: Let this unit March at an average speed of X km/h on the first day and Y km/h on the second day.

According to the meaning of the question: 4x+5y=98 ①.

5y-4x=2 ②

Solve this system of equations, x= 12.

y= 10

Answer: The average marching speed of this unit on the first day is 12 km/h, and the average marching speed on the second day is

10 km/h

4. Solution: Using X pieces of paper as the box body and Y pieces of paper as the box bottom can make the box body and the box bottom just match. According to the topic

Meaning, meaning: x+y=36 ①

2×25x=40y ②

Solve this system of equations, x= 16.

y=20

Answer: The box is made of 16 pieces of iron, and the bottom of the box is made of 20 pieces of iron, which is just the same.

5. solution: the cart can transport x tons at a time, and the car can transport y tons at a time.

Meaning, meaning: 2x+3y= 15.5 ①

5x+6y=35 ② Solve this equation group and get: x=4.

y=5/2

Therefore, 3x+5y = 3x4+5x5 (5/2) = 24.5 tons.

A: Three big cars and five small cars can transport 24.5 tons at a time.

6. solution: let the slope distance be x km and the horizontal distance be y km. According to the meaning of the question, we can get:

x/3+y/4=54/60 ①

y/4+x/5=2/60 ②

To solve this system of equations, x= 1.5.

y= 1.6

X+y =1.5+1.6 = 3.1(km)

Answer: The whole journey from A to B is 3. 1km.

7、

Solution: Suppose you need to take 30% and 75% liquid medicine x kg, y kg, according to the meaning of the question, you can get:

x+y= 18

30%x+75%y= 18×50%

Solve this system of equations, x= 10.

y=8

Answer: You need to take 30% liquid medicine 10kg and 75% liquid medicine (8kg).

8、

Solution: Suppose the unit price of commodity A before discount is X yuan, and commodity B is Y yuan. According to the meaning of the question, it is concluded that:

60x+30y= 1080 ①

50x+ 10y=840 ②

Solve this system of equations, x= 16.

y=4

So 500× 16+500×4-9600=400 (yuan).

It's cheaper than no discount, 400 yuan.

9. Solution: Wrong. The reasons are as follows: the price of a toothpaste is X yuan, and the price of a toothpaste is Y yuan.

According to the meaning of the question, it means: 39x+2 1y=396, which means 13x+7y= 132, so

52x+28y = 39x+21y+13x+7y = 396+132 = 528 (yuan)

This record is wrong because of 5 18≠528.