Answers

  • Brainly User
2016-01-17T16:34:35+08:00
Present ages:
Margaret = x
Kevin = x + 4

Ages next year (+1):
Margaret = x + 1
Kevin = x + 4+1    ⇒    x + 5

Equation:
x + 5 = 2(x + 1)
x + 5 = 2x + 2
x - 2x = 2 - 5
-x = -3
-1(-x = -3) -1
x = 3

Substitute 3 to x:
Present ages:
Margaret = x  ⇒  3 years old
Kevin = x + 4  ⇒  3 + 4 = 7 years old

ANSWER:  Kevin is 7 years old.

Check their ages next year:
Margaret: 3 + 1 = 4 years old
Kevin: 7 + 1 = 8 years old

Next year, Kevin will be 2 times as old as Margaret:
8 = 2 (4)
8 = 8      True
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2016-01-17T17:13:42+08:00
Let x = Margaret's age (present)
x + 4 = Kevin's age (present)

Therefore..
x + 1 = Margaret's age (next year)
x + 4 + 1 = x + 5 = Kevin's age (next year)

2(x + 1) = x + 5
2x + 2 = x + 5
2x - x = 5 - 2 
x = 3 - Margaret's age (present)
x + 4 = 3 + 4 = 7 - Kevin's age (present)

Answer: 7 yrs. old

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