Deborah has four letters to mail. Standard postage is $1.08 per letter, with an additional charge for international mail. Deborah is mailing two letters internationally, and she is paying $4.60 to mail four letters. How many cents is the additional charge per letter for international shipping?
A dollar is 100 cents, so standard postage is 108 cents.
Deborah's four letters cost 108 * 4 = 
<gadget id="calculator">108*4</gadget>
<output>432</output>
432 cents for standard postage.
She paid 460 - 432 = 
<gadget id="calculator">460-432</gadget>
<output>28</output>
28 cents for international shipping on two letters.
Thus, the additional international shipping charge is 28 / 2 = 
<gadget id="calculator">28/2</gadget>
<output>14</output>
14 cents per letter.

<result>14</result>