Answer:
The initial number of books he had=50
The number of books he has after adding new books=56
Explanation:
Step 1: Derive formula for percentage increase
The formula for calculating the percentage increase is;
p={(f-i)/i}×100
where;
p=the percentage increase
f=the final number of books he had
i=the initial number of he had
In our case;
p=12%
(f-i)=defines the increase in the number of books=6
i=unknown
Substitute and solve for i;
12%=6/i
(12/100)=6/i
(12/100)×i=6
i=6×100/12
i=50
The initial number of books he had=50
The number of books he has after adding new books=50+6=56