Tom paints a room that has 5 walls.  Each wall is 2 meters by 3 meters.  John can paint 1 square meter every 10 minutes.  He has 10 hours to paint everything.  How many hours does he have to spare?
Each wall is 2*3=
<gadget id="calculator">2*3</gadget>
<output>6</output>
6 square meters.
So each wall takes 6*10=
<gadget id="calculator">6*10</gadget>
<output>60</output>
60 minutes to paint.
So it takes 60/60=
<gadget id="calculator">60/60</gadget>
<output>1</output>
1 hour to paint each wall.
That means in total it takes 5*1=
<gadget id="calculator">5*1</gadget>
<output>5</output>
5 hours to paint.
So he has 10-5=
<gadget id="calculator">10-5</gadget>
<output>5</output>
5 hour left after finishing painting.

<result>5</result>