Expressing ages

The total age for Amelia, Bernard, and Cindy is 10w years.  Amelia is 2w years old.  Bernard is as old as Cindy.
Express Cindy's age in terms of w. If w = 4, how old is Cindy? ​

Amelia + Bernard + Cindy = 10w   {the total of their ages is 10w}
2w + ? + ? = 10w   {Amelia is 2w years old, Bernard and Cindy are the same}
? + ? = 8w   {subtracted 2w from each side}
2? = 8w   {added ? and ?}
? = 4w   {divided each side by 2} 

Cindy is 4w 

If w = 4,
4w 
= 4(4)   {substituted 4 in for w}
= 16    {multiplied} 

If w = 4, then Cindy is 16

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