While on vacation, Erika bought 6 postcards, which was twice as many postcards as Nathan bought. Samantha bought 4 times as many postcards as Nathan. how many postcards did Samantha buy?

The answer is 12, I believe.

Write a system of equation based on the problem

⇒ Erika bought 6 postcards

E = 6

⇒ Erika bought twice as many postcards as Nathan bought

E = 2N

2N = E

⇒ Samantha bought 4 times as many postcards as Nathan

S = 4N

Before we find the number of Samantha's postcards, we need to find the number of Nathan's postcard. Substitute E with 6 in the second equation.

2N = E

2N = 6

N = 6/2

N = 3

Nathan bought 3 postcards

Find the number of Samantha's postcard

Substitute N with the number of Nathan's postcards, which is 3, in the third equation

S = 4N

S = 4 * 3

S = 12

Samantha bought 12 postcards