Question 1129740
x students
cost per ticket is 39-0.1x
cost of everything is 160 + x(39-0.1x)
average cost is (160+39x-0.1x^2)/x
that has to be <=39
multiply through by x
160+39x-0.1x^2-39x<=0
x^2>=1600
x>=40
For 40 students, cost is $35.00 per student or $1400 for 40 students and with bus $1560
The average cost is $39.

40.