Grayson has 100 questions on a test. He answers some of the questions for 2 hours, taking two minutes for each answer, then realizes he doesn't know the rest of the questions. How many questions does Grayson leave unanswered when he submits his test?
Each hour contains 60 minutes, so after 2 hours he took 2*60 = 
<gadget id="calculator">2*60</gadget>
<output>120</output>
120 minutes.
If each question takes two minutes, then he answered 120/2 = 
<gadget id="calculator">120/2</gadget>
<output>60</output>
60 questions.
Unanswered questions is 100-60 = 
<gadget id="calculator">100-60</gadget>
<output>40</output>
40 questions.

<result>40</result>