His total expenditure so far is $50+$35+$15 = $<<50+35+15=100>>100
To make a profit of 10%, he has to make a total of $100+($100*(10/100) = $<<100+(100*(10/100))=110>>110 from sales
To make $110 from the sales of 10 bags, each bag should cost $110/10 = $<<110/10=11>>11
#### 11