Sally and Marta had the same number of postcards. After Sally sold 18 of her postcards, Marta had 4 times as mow postcards as Sally. How many postcards did each girl have to begin with?

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Answer 1 · 2015-11-13T11:06:27

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Answer 2 · 2015-11-13T11:12:51

Each girl had 24 postcards.

Let the number of postcards with Sally and Marta be $x$ $x$ .

After selling 18 postcards Sally had $x$ $x$ - 18 postcards.

Then Marta will have 4 times of Sally.

4( $x - 18$ $x-18$ ) = $x$ $x$

$4 x$ $4x$ - $72$ $72$ = $x$ $x$

Subtracting $x$ $x$ on both sides

$4 x$ $4x$ - $x$ $x$ - $72$ $72$ = $x$ $x$ - $x$ $x$

$3 x$ $3x$ - $72$ $72$ = $0$ $0$

Adding 72 on both sides

$3 x$ $3x$ - $72$ $72$ + $72$ $72$ = $0$ $0$ + $72$ $72$

$3 x$ $3x$ = $72$ $72$

Dividing both sides by 3

$3 \frac{x}{3}$ $3x/3$ = $\frac{72}{3}$ $72/3$

$x$ $x$ = 24

Hence each girl had 24 postcards in the beginning.