8 years ago James was twice Janet's age.  In 15 years James will turn 37.  Susan was born when Janet turned 3.  How old will Susan turn in 5 years?
James is 37-15=
<gadget id="calculator">37-15</gadget>
<output>22</output>
22 years old.
So 8 years ago he was 22-8=
<gadget id="calculator">22-8</gadget>
<output>14</output>
14 years old.
That means Janet was 14/2=
<gadget id="calculator">14/2</gadget>
<output>7</output>
7 years old 8 years ago.
So Janet is now 7+8=
<gadget id="calculator">7+8</gadget>
<output>15</output>
15 years old.
That means Susan is 15-3=
<gadget id="calculator">15-3</gadget>
<output>12</output>
12 years old.
So in 5 years she will be 12+5=
<gadget id="calculator">12+5</gadget>
<output>17</output>
17 years old.

<result>17</result>