She bought 8 bags of candy since 10 multiplied by eight is 80 and 8 is two less than ten.(ten candies in each bag)
6p+p+2-3=8p-8
7p-1=8p-8
1=1p-8
7=1p
p=7
Given parameters:
Cost price of the article = Nu.28.30
Selling price of the article = Nu.29.30
Unknown:
Gain percentage = ?
The gain percentage is the same as the percentage profit on a trade.
The formula is given as:
Gain percentage = 
Profit = Selling price - Cost price
= Nu.29.30 - Nu.28.30
= Nu. 1
Now input the parameters and solve;
Gain percentage = 
= 3.5%
The gain percent is 3.5%