If you double a number and add 5 to the result, then that's 20 more than half of the original number. What's the original number?
Let x be the original number.
2*x+5=20+x/2
2*x-x/2=15
4*x-x=30
3*x=30
x=
<gadget id="calculator">10</gadget>
<output>10</output>
10.

<result>4</result>