The 7/8 pound fish.
2/3lb = 0.6666 lb
7/8lb = 0.875 lb
so since only 3 out of 11 went to visit then it is simple
since just 3 went and there were 11
3/11 of the students went
30% = .3
.3(24.40a + 14.50c)
24.40 = cost of adult ticket
14.50 = cost of child ticket
a = # of adult tickets sold
c = # of child tickets sold
.3 * 24.40a + .3 * 14.50c
answer: 7.32a + 4.35c