Question 1003852
let the fraction of the students in class that play soccer be {{{a/b}}} and the fraction of the students in class that play basketball be {{{c/d}}}

then, {{{1=a/b+c/d}}} 

if at the class party {{{a/b=1/3}}} of the students play soccer,{{{1-1/3=c/d}}}

 {{{c/d=1-1/3=3/3-1/3=2/3}}} 

so, {{{2/3}}} of the class plays basketball