Question 996415
1. A father is 34 years old and his son is 12 years old. In how many years will the father be twice as old as his son.
let x=number of years father will be twice as old as his son.
34+x=2(12+x)
34+x=24+2x
x=10
number of years father will be twice as old as his son=10
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2. Sam is 18 and Bill is 24. How many years ago was Bill three times as old as her Sam?
let x= How many years ago was Bill three times as old as her Sam.
24-x=3(18-x)
24-x=54-3x
2x=30
x=15
 How many years ago was Bill three times as old as her Sam. 15
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 3. John has four times as many marbles as Peter. If he gives Peter 8 marble he will have twice as many marble as Peter. How many did each have originally.
let x=number of marbles Peter had originally
4x= number of marblesJohn had originally
4x-8=2(x+8)
4x-8=2x+16
2x=24
x=12
number of marbles Peter had originally=12
4x= number of marblesJohn had originally=48

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4. The sum of two numbers is 17, and three times the smaller is 3 more than the bigger, Find the numbers.
let x=larger number
17-x=smaller number
3(17-x)=3+x
51-3x=3+x
4x=48
x=12
larger number=12
smaller number=5
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5. If each stroke of a pump removes 20% of the air in the cylinder, what percentage of the air will be left after the third stroke? 40%