2+number won over 9+number played=1/2
number won=number played (number played means how many more past 9)
so
if n=number won=number played then[tex] \frac{2+n}{9+n}= \frac{1}{2} [/tex]
times both sides by (2)(9+n)
2(2+n)=9+n
distribute
4+2n=9+n
minus n from both sides
4+n=9
minus 4 from both sides
n=5
answer is 5
test
2+5=7
9+5=14
7/14=1/2
true
n=5