SELECT count(*) FROM tryout WHERE decision  =  'yes'
How many students received a yes from tryouts?
[Schema (values) (types)]: | soccer_2 |  College : cname (text) , state (text) , enr (text) | Player : pid (text) , pname (text) , ycard (text) , hs (number) | Tryout : pid (text) , cname (text) , ppos (text) , decision (number);