Answer:
There are 60 tech workers altogether
Step-by-step explanation:
Let X be the total number of tech workers in the company
Out of X tech employees, 20 % applied for leaves
In totality, 12 tech employees are on leave
Thus,

On solving the above mathematical equation, we get -

Hence, there are 60 tech workers altogether
'a', 'c', and 'd' are true for any two circles. That's because
ALL circles are similar. You don't need to prove it. The question
is weird.
30/78 simplified is 15/39