In four years, Suzy will be twice Mary's age then. If Suzy is 20 now, how old is Mary?
In four years, Suzy will be 20+4=
<gadget id="calculator">20+4</gadget>
<output>24</output>
24.
Then Mary will be 24/2=
<gadget id="calculator">24/2</gadget>
<output>12</output>
12.
Then Mary is now 12-4=
<gadget id="calculator">12-4</gadget>
<output>8</output>
8.

<result>8</result>