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Barbara's sister is twice as old as Barbara. Barbara's sister is 7 years younger than Barbara's brother. If Barbara's brother is 21, which equation could be used to find Barbara's age (b)?

Barbaras sister is twice as old as Barbara Barbaras sister is 7 years younger than Barbaras brother If Barbaras brother is 21 which equation could be used to fi class=

Respuesta :

Answer:

Option D

Step-by-step explanation:

Let the age of Barbara sister = x years

And the age of Barbara's brother = y years

"Barbara's sister is 7 years younger than Barbara's brother"

x = y - 7

If y = 21,

x = 21 - 7 ------(1)

"Barbara's sister is twice old as Barbara"

x = 2b --------(2)

By substituting the value of x from equation (2) to equation (1),

2b = 21 - 7

2b + 7 = 21 + 7

2b + 7 = 21

Therefore, Option D will be the answer.

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