Sally 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?
s=m
m = 4(s-18)
Each had 24
To solve this problem, let's use algebraic equations. Let's assume that Sally and Marta each had x number of postcards initially.
According to the problem, after Sally sold 18 postcards, Marta had 4 times as many postcards as Sally. This can be written as an equation:
Marta's postcards = 4 * (Sally's postcards - 18)
Substituting x for the number of postcards initially, we have:
4 * (x - 18) = x
Now, let's solve for x.
Distributing the 4:
4x - 72 = x
Subtracting x from both sides:
3x - 72 = 0
Adding 72 to both sides:
3x = 72
Dividing by 3:
x = 24
So, Sally and Marta each had 24 postcards initially.