7×( 16+x)=9×( 16-x)
X = 2km/h is obtained from the solution.
The water flow speed is 2 km/h.
2. If the number of questions answered incorrectly is x, the number of unanswered questions is 2x, and the number of questions answered correctly is (25-3x).
Get the equation according to the meaning of the question
4×(25-3x)-2×x=86
For solution, X= 1, for 25-3x, x = 22.
22 correct answers
3. Let the number in the tenth place be X, then the number in the hundredth place is x- 1, and the number in the unit place is 3x+2.
Get the equation according to the meaning of the question
x+x- 1+3x+2 = 1 1
X=2, so the percentile is 2- 1= 1, and the unit digit is 3×2+2=8.
So this three-digit number is 128.
4. If the length is x cm and the width is (24-x) cm, the equation is obtained according to the meaning of the question.
[x-(24-x)]x = 0.4
X= 15, so the width is 24- 15=9.
Design length 15cm, width 9cm.
5、3(3x+7)-2(2x- 1)=8
X=-3 is the solution.
6.①y 1=y2 means 1/2x- 1=2/3x-3. Just solve this equation. I don't understand. Is x on the denominator?
②y 1 and y2 are opposite numbers, that is, y 1=-y2, that is, 1/2x- 1=-2/3x+3. I still don't understand whether x is on the denominator.
Multiple choice
Question 1 answer: 3, -8
The answer to the second question: 2
The answer to the third question: 80, 82, 84
The answer to the fourth question: 3x+ 14-x-5= 19, which is 2x- 10=0 after finishing.
The answer to the fifth question: x÷6-(x-2×4)÷4= 1/4, and it will be x-2 1=0 after completion.
Typing dizzy! The above answers are for reference only! 0 points, poor!