A problem for the application of a system of binary equations

Answer x correctly, answer y incorrectly.

4x-y=74

25-x-y-y=2

x=19y=2

Then he answered 19 questions correctly.

He got 19 questions right; You can list three formulas, let x be the correct answer, y is not answered, and z is the wrong answer, then there is: x+y+z=25; y-z=2;4x-z=74, the answer can be obtained from these three equations.

Answer x questions correctly, answer y questions incorrectly, and don't answer z questions.

4x-y=74 (1)

z=y+2 (2)

x+y+z=25 (3)

x=19

19.If you answer question A correctly and answer question B incorrectly, you will not answer b+2, 4a-b=74, a+b+(b+2)=25, a=19

19 channels. 19x4=76

2 points will be deducted for 2 incorrect answers.

There are 4 questions that I didn't answer.

There are 2 more questions that are not answered than those that are incorrect.

Solution: Suppose he answered correctly in the X path and answered the wrong in the y way, according to the meaning of the question, he gets:

4x-y=74

x+y+(y+2)=25

Solution: x=19

y=2 unanswered questions: 25-19-2 4 (channels).

Set up an electronic whiteboard is the first is x yuan, and the first of a projector is y yuan, according to the problem to get the following equations.

2x-3y=4000 (1)

4x+3y=44000 (2)

1) +(2) 6x=48000 => x=8000 (yuan) substitute x=8000 (yuan) into (1), get y=4000 (yuan) Answer: The ** of an electronic tabula rasa is 8000 yuan, and the ** of a projector is 4000 yuan.

Solution: If the area of the forest farm is x hectares, the pasture area is 20%x hectares x + 20%x = 162

x=13520%x=135*20%=27

A: After completion, the forest farm area is 135 hectares and the pasture area is 27 hectares.

After the completion of the forest farm x hectares, pasture y hectares, then:

x+y=162

20%x=y

Substituting y=into x+y=162 Yes.

The solution is x=135

So y=162-135=27

So the area of the forest farm is 135 hectares and the pasture area is 27 hectares.