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2014-11-23T21:41:49+08:00

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X=selma 4x=fred 4x+10=2(x+10) 4x+10=2x+20 2x=10 X=5 Thefore selma is 5 years old and fred is 20 years old. Hope this helps =)
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2014-11-24T10:38:41+08:00
Let Fred be x and Selma be y

Fred is 4 times as old as his niece, Selma

x = 4y

10 years from now, he will be twice as old as she will be.

x + 10 = 2(y + 10)

Let us now substitute the value of x to the second equation

4y + 10 = 2(y + 10)

Multiply

4y + 10 = 2y + 20

Transpose 10 and 8y

4y - 2y = 20 - 10

Subtract

2y = 10

Divide both by 2

2y/2 = 10/2

Therefore

y = 5 (Selma is 5 years old)

Let us now determine the age of Fred

x = 4y

Substitute the value of y

x = 4(5)

Therefore

x = 20

Selma is 5 years old and Fred is 20 years old

I hope it helps
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