One customer paid $12 for 14 postcards and 5 large envelopes. Another customer paid $24.80 for 10 postcards and 15 large envelopes. What was the cost in dollars of each large envelope?

$1.42

Step-by-step explanation:

Since, The first customer paid $12 for 14 postcards and 5 large envelopes.

That is, 14 x + 5 y = 12         (1)

And, The second customer paid $24.80 for 10 postcards and 15 large envelopes.

That is, 10 x + 15 y = 24.80  (2)

3 × equation (1),

We get, 42 x + 15 y = 36 (3)

Equation (3) - Equation (2)

32 x = 11.20

⇒ x = 11.20/32

⇒ x = 0.35

By putting the value of x in equation (1),

We get, 14 × 0.35 + 5 y = 12

⇒ 4.9 + 5 y = 12

⇒ 5 y = 7.1

⇒ y = 1.42

Thus, the cost of one postcard = $ 0.35

And, the cost of each large envelope = $ 1.42

do i do it on a graph?

step-by-step explanation:

tube or goog would be a great resource to with that question