In 5p 1 A

in 1P 1/5 A similarly in 1p 1/3 B and in 1p 3C

So in 3 P 1/5 A+1/3 B+ 3C

In 100p 33/5 A+33/3 B+ 33*3 C nearly equals 7A+11B+99C

Quantity 117 Birds.we have to get 100birds.So deduct 17Birds of Type C

Cost of 17 bird 17*1/3(take 18 so 18/3 6Pound)

But cost for 7A+11B+99C 101 1A we can add.

ans 8A+11B+81C

Solutions area b c are in order 4 18 788 11 8112 4 84

Explanation a+b+c

100-(e1)5a+3b+c/3

100-(e2)3(e2)-(e1)14a+8b

200 or 7a+4b

100

Substitute a with any value so that b must be a round digit

There can be only 3 values for a i.e 4 8 12 which gives b as 18 11 4 respectively

Substitute a b in (e1) and get value of c

I am saying this so that we wont waste our time to find other solutions like i did...