MyApproach
$3/10$ of the members have passed the test.
$\implies 7/10$ of the members have not passed the test.
Out of $7/10$ of the members, $12$ have taken preparatory course and $30$ have not taken preparatory course.
$\implies 7/10\cdot X=30+12$ where $X$ are the total no of people.
$\implies X=60$
Am I correct in my approach?
Shortly,
$\frac 7{10}th$ of total =$30+12$
So,total=$60$