(4+04 of 65438? Students from a summer camp of science and technology in a school, led by three teachers, are going to visit Peking University and experience university life. Existing.

() There are * * * students in this school attending the summer camp for science and technology.

QQ QQ x dq% = QQ (x+3) x 7q%，

Solution: x= x,

A: There are * * * students in this school attending the summer camp for science and technology.

(a) Assuming that the total number of students is A, it is concluded from the meaning of the question:

If you want the travel agency to be cost-effective, QQ QA× dq% < QQ (a+3 )× 7q%,

Solution: a < a,

If you choose a youth travel agency with high cost performance, then QQ × dq% > QQ (a+3) × 7q%,

Solution: a >,

Therefore, if more students are added, schools should choose youth travel.