Question

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

Answer 1

`x-number\ of\ postcards\\\\4(x-18)=x\\\\4x-72=x\\\\4x-x=72\\\\3x=72\ \ \ \ \ |:3\\\\x=24\\\\Each\ of\ them\ had\ 24\ postcards.`