Question #b6c11

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Answer 1 · 2017-10-18T18:09:01

See a solution process below{

Let's call the age of the younger sister: $a$

Then, the age of the older sister is: $2a$

If the sum of their ages is $12$ we can write this equation and solve for $a$ :

$a + 2a = 12$

$1a + 2a = 12$

$(1 + 2)a = 12$

$3a = 12$

$(3a)/color(red)(3) = 12/color(red)(3)$

$(color(red)(cancel(color(black)(3)))a)/cancel(color(red)(3)) = 4$

$a = 4$

The younger sister is: 4 years old.

The older sister is: $2 xx 4 =$ 8 years old.