Question 136628
Right now they are 18/40 in winning percentage. 
How many games do they need to win out of 50 to have a percentage of 2/3. 
Let x be the number of games they need to win.
Then their winning percentage will be,
{{{(18+x)/(40+50)=2/3}}}
{{{(18+x)/90=2/3}}}
{{{18+x=(2/3)(90)}}}
{{{18+x=60}}}
{{{x=60-18}}}
{{{x=42}}}
Check your answer.
If they play 50 games and win 42, their wins will increase to 60 and their total games played will increase to 90. 
Their winning percentage will be 60/90 or 2/3. 
Correct answer.