Rosie runs 6 miles per hour. She runs for 1 hour on Monday, 30 minutes on Tuesday, 1 hour on Wednesday, and 20 minutes on Thursday. If she wants to run 20 miles for the week, how many minutes should she run on Friday?
On Monday and Wednesday, Rosie runs 6*1= 
<gadget id="calculator">6*1</gadget>
<output>6</output>
6 miles.
On Tuesday, Rosie runs 6*(30 minutes/60 minutes) = 
<gadget id="calculator">6*(30/60)</gadget>
<output>3</output>
3 miles.
On Thursday, Rosie runs 6*(20 minutes/60 minutes)=
<gadget id="calculator">6*(20/60)</gadget>
<output>2</output>
2 miles.
So far this week Rosie has run 6+3+6+2=
<gadget id="calculator">6+3+6+2</gadget>
<output>17</output>
17 miles.
To reach her goal, she must run 20-17=
<gadget id="calculator">20-17</gadget>
<output>3</output>
3 miles on Friday.
Thus, she should run for 6/3=.5 hour which is 30 minutes.

<result>30</result>