David has a number in mind. He multiplies it by 3, then subtracts 7 form the product. He gets 53. What is the number?
The sum of the ages of afather and his son is 100. The father is 28 years older then the son. guess the ages of the father and the son.
please answer the math question
2007-08-17 7:59 pm
回答 (2)
2007-08-17 8:12 pm
✔ 最佳答案
Let x be the number . 3x-7=53
3x=53+7
3x=60
x=20
∴ The number is 20 .
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Let x be the age of the son .
x+(x+28)=100
x+x+28=100
2x=100-28
2x=72
x=36
∴ The son is 36 years old and the father is 64 years old .
2007-08-17 8:35 pm
1. Suppose the number is Y
Y x 3-7=53
3Y =53+7
3Y=60
Y=20
You got the number is 20.
2. Suppose the age of the sun is M, so the age of his father is (28+M)
M + (28+M)=100
2M=100-28
M=36
so you got the age of the sum is 36
the age of his father 28+M=28+36=64
Y x 3-7=53
3Y =53+7
3Y=60
Y=20
You got the number is 20.
2. Suppose the age of the sun is M, so the age of his father is (28+M)
M + (28+M)=100
2M=100-28
M=36
so you got the age of the sum is 36
the age of his father 28+M=28+36=64
參考: myself
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