Jenine can sharpen a pencil 5 times before it runs out. She needs to sharpen a pencil for every 1.5 hours of use. She already has ten pencils and needs to write for 105 hours. A new pencil costs $2. How much does she need to spend on more pencils to be able to write for 105 hours?
A pencil last 7.5 hours because 5 x 1.5 = 
<gadget id="calculator">5*1.5</gadget>
<output>7.5</output>
7.5.
The pencils she has will last 75 hours because 10 x 7.5 = 
<gadget id="calculator">10*7.5</gadget>
<output>75</output>
75.
She needs 30 more hours of writing because 105 - 75 = 
<gadget id="calculator">105-75</gadget>
<output>30</output>
30.
She will need 4 more pencils to reach this because 30 / 7.5 = 
<gadget id="calculator">30/7.5</gadget>
<output>4</output>
4.
She will spend $8 on pencils because 4 x 2 = 
<gadget id="calculator">4*2</gadget>
<output>8</output>
8.

<result>8</result>