It would cost <em>n</em> people $<em>nd</em> to play Decimal Decisions and $<em>nr</em> to play Ratio Rage. So, it would cost <em>n</em> people $<em>nd</em> + $<em>nr</em>= $2<em>n</em>(<em>d</em> + <em>r</em>).
<em>d</em>= Decimal Decisions and <em>r</em>= Ratio Rage
You didn't give a price for either game, so I just did variables in place of actual cost. Hope this helps!