Three years ago, Bethany was twice the age of her younger sister. In 5 years, her younger sister will be 16. How old is Bethany now?
First find how old Bethany's sister currently is: 16 years - 5 years = 
<gadget id="calculator">16-5</gadget>
<output>11</output>
11 years.
Then find how old her sister was 3 years ago: 11 years - 3 years = 
<gadget id="calculator">11-3</gadget>
<output>8</output>
8 years.
Then double that age to find how old Bethany was three years ago: 8 years * 2 = 
<gadget id="calculator">8*2</gadget>
<output>16</output>
16 years.
Then add 3 years to that number to find how old Bethany is now: 16 years + 3 years = 
<gadget id="calculator">16+3</gadget>
<output>19</output>
19 years.

<result>19</result>