William and Harry played 15 rounds of tic-tac-toe.  William won 5 more rounds than Harry.  How many rounds did William win?
They played 15 rounds and William won 5 more rounds than Harry so that leaves 15 - 5 = 
<gadget id="calculator">15-5</gadget>
<output>10</output>
10 round.
There are 2 players and 10 rounds so they each won 10/2 = 5 rounds.
William won 5 more rounds than Harry and they each won 5 rounds so William won 5+5 = 
<gadget id="calculator">5+5</gadget>
<output>10</output>
10 rounds.

<result>10</result>