Nick's cell phone was initially empty but was then charged for 45 minutes and has reached a 25% charge. How much longer must the cell phone be charged to reach 100% charge?
The ratio between the time charged and the time to be charged is 100 / 25 = 
<gadget id="calculator">100/25</gadget>
<output>4</output>
4.
To reach 100%, the cell must be charged for 45 minutes * 4 = 
<gadget id="calculator">45*4</gadget>
<output>180</output>
180 minutes.
Subtracting the 45 minutes that Jimmy already used to charge the cell phone, there are still 180 - 45 =
<gadget id="calculator">180-45</gadget>
<output>135</output>
135 minutes of charging time left.

<result>135</result>