James has a room that is 13 feet by 18 feet.  He increases each dimension by 2 feet.  He then builds 3 more rooms of equal size and 1 room of twice that size.  How much area does he have?
He increases the length to 13+2=
<gadget id="calculator">13+2</gadget>
<output>15</output>
15 feet.
He increases the width to 18+2=
<gadget id="calculator">18+2</gadget>
<output>20</output>
20 feet.
So the rooms are 15*20=
<gadget id="calculator">15*20</gadget>
<output>300</output>
300 square feet.
So he has 1+3=
<gadget id="calculator">1+3</gadget>
<output>4</output>
4 rooms of this size.
So he has 4*300=
<gadget id="calculator">4*300</gadget>
<output>1_200</output>
1200 square feet of rooms this size.
He also has one room of size 300*2=
<gadget id="calculator">300*2</gadget>
<output>600</output>
600 square feet.
So he has 1200+600=
<gadget id="calculator">1200+600</gadget>
<output>1_800</output>
1800 square feet of rooms.

<result>1_800</result>