Sara sent letters to her friend in China every month. She sent 6 letters in January, 9 letters in February, and in March she sent triple the number of letters she sent in January. How many letters does Sara send?
Combining January and February, Sara sent 6 + 9 = 
<gadget id="calculator">6+9</gadget>
<output>15</output>
15 letters.
In March, she sent 3 * 6 = 
<gadget id="calculator">3*6</gadget>
<output>18</output>
18 letters.
Altogether, Sara sent 15 + 18 = 
<gadget id="calculator">15+18</gadget>
<output>33</output>
33 letters.

<result>33</result>