# 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?

Nov 13, 2015

Nov 13, 2015

#### Explanation:

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

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

Then Marta will have 4 times of Sally.

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

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

Subtracting $x$ on both sides

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

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

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

$3 x$ = $72$

Dividing both sides by 3

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

$x$ = 24

Hence each girl had 24 postcards in the beginning.