James has 20 years of experience.  8 years ago John had twice as much experience as James.  Mike started when John had 16 years of experience.  What is their combined experience?
8 years ago James had 20-8=
<gadget id="calculator">20-8</gadget>
<output>12</output>
12 years.
So 8 years ago John had 12*2=24 years experience.
That means John has 24+8=
<gadget id="calculator">24+8</gadget>
<output>32</output>
32 years experience.
So Mike has 32-16=
<gadget id="calculator">32-16</gadget>
<output>16</output>
16 years of experience.
So together they have 20+32+16=
<gadget id="calculator">20+32+16</gadget>
<output>68</output>
68 years experience.

<result>68</result>