Question 303214
{{{n/5=p+4}}}, where p is an integer.
{{{n=5p+20}}}
.
.
.
{{{(n+a)/5=n/5+a/5=p+4+a/5=q+a/5}}}, where q is an integer.
{{{a/5=2/5}}}
{{{a=2}}}
so then b) is the correct answer.