Solve blue x=6 1, then red 3x+8= 19 1, and green x- 1=60.
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2. There are X people, so the dormitory is x- 10 (each room 1 person,1person has no place to live).
X/3 + 10=x- 10。
The number of solvers x=30, and the dormitory x- 10=20.
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3. If there are x girls, there are 15-x boys.
Have (x-3)*2= 15-x
X=7 for girls and 15-x=8 for boys.
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4. Solution: Let ten digits be x, then one digit is11-x.
The original two digits are 10x+( 1 1-x), and the new two digits after switching are10 * (11-x)+x.
Yes10 * (11-x)+x-10x+(11-x) = 63.
X=2, so 1 1-x=9, so the original two-digit number is10x+(1/-x) = 29.
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5. Solution: Suppose Uncle is X years old this year, then Xiaoming is x-30 years old this year.
Have (two years ago) (x-30)-2*4=x-2? Xiao Qiang's age is 4 1 of his uncle's, which is a quarter?
Solve x=
6. Solution: If the ship's still water speed is X, then downstream is x+3 and downstream is x-3.
Yes (the total distance of AB is constant) 5*(x+3)=7.5*(x-3).
Solve x= 15
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7. Solution: Assume that B has worked for X days, the total amount of work is 1, the efficiency of A is 1/20, and the efficiency of B is110.
Yes110 * x+1/20 * (12-x) =1.
Solve x=8
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8. Solution: If the set price is X, then the original price is 0.75*x+25 or 0.9*x-20.
There is 0.75*x+25=0.9*x-20.
Solve x=300
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9. let the cost price be x,
Yes165 * 0.9-x =10% * x.
Solve x= 135
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10, the number between columns is x, the difference between columns of the calendar is 1 day, and the difference between columns is 7 days (exactly one week).
There is (x-7)+x+(x+7)=30.
Solve x= 10, so x-7=3 and x+7= 17.
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1 1, (1) solution: moving in the opposite direction is the sum of speeds.
280/(60+80)=2h
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(2) Solution: Walking in the same direction is a pursuit problem, not a speed difference problem.
280/(80-60)= 14h
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Other issues
1, (1) solution: Because the runway is circular (circular), it can be regarded as the opposite direction of a straight line (find the speed sum), and the distance is exactly the length of the runway.
400/(9+7)= 25 seconds
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(2) Solution: Because the runway is circular and travels in the same direction, it can be regarded as a straight line traveling in the same direction (finding the speed difference), and the distance is exactly the length of the runway.
400/(9-7)= 200 seconds
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2. Solution: It is found that the price consists of three parts, the front is integer multiple 3 times+middle decimal multiple 0.5 times+last 0. 1.
So y=3*x+0.5x +0. 1.
=3.5x+0. 1
Bring y=56. 1 in and get x= 16.
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