I really hate it when people do stuff like "bananas (B) and nuts(N)". B and N are numbers, not "bananas" or "nuts". Often it doesn't make any difference but here- are B and N the weight, in kg, of bananas and nuts bought or the amount of money, in dollars, paid for them?
The first equation you give, and happyg1 approves, is B+N=133.10, apparently from "A zookeeper spends $133.10 altogether on bananas and nuts". Since 133.10 is dollars, I must presume that "B" is the amount spent on bananas and "N" the amount spent of nuts.
And then you give "N+8=B", apparently from "He buys 8 kilograms more bananas than nuts". Which means you are taking "N" and "B" now to be weight in kg.
You can't have it both ways! I'm sorry but it looks to me like happyg1 is leading you down the wrong path.
Start by stating explicitely what your letters stand for: N= weight of nuts bought in kg, B= weight of bananas bought in kg. Now you can say: B= N+ 8.
Since "Bananas cost $2.20 per kilogram and nuts cost $4.80 per kilogram", B kg of bananas will cost 2.20B dollars and N kg of nuts will cost 4.80N. B kg of bananas and N kg of nuts will cost 2.20B+ 4.80N dollars and we are told that the zookeeper spent 133.10 dollars total: 2.20B+4.80N= 133.10.
Your two equations are B= N+ 8 and 2.20B+ 4.80N= 133.10.
