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Mary's age is twice her brother's age and half her sister's age. How old is Mary, in years, if the sum of the three ages is 28 years?

 Mar 3, 2021
 #1
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ayo crypto

 Mar 3, 2021
 #3
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Who are you?

cryptoaops  Mar 3, 2021
 #4
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addie ofc

Guest Mar 3, 2021
 #5
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Hm, make an acct and message (web2.0calc.com/messagecenter/cryptoaops). talk like that instead.

cryptoaops  Mar 3, 2021
 #2
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+2

Let Mary's  age  = M

Her brother's age =  M/2

Her sister's age = 2M

 

So

 

M    + M/2   +  2M    = 28               simplify

 

3.5M =  28       divide both sides by  3.5

 

M =  8     ( Mary is  eight years old )

 

cool cool cool

 Mar 3, 2021

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