A4. Aunt Micka is giving chocolates to all her nephews and nieces. If she gives each of them 5 chocolates, she will have 13 chocolates left; if she gives each of them 7 chocolates, she will have only three left. How many nephews and nieces does Aunt Micka have?
(A) 3
(B) 4
(C) 5
(D) 6
(E) 10
A4. Let the number of boys and girls be denoted by $x$ and write the equation $5 x+13=7 x+3$. The solution to the equation is $x=5$.