The sum of 5 numbers is 5 x 18.4=92
The sum of the first three numbers = 12 x 3=36
Therefore the sum of the last two numbers= 92-36=56
The sum of the last three numbers = 30 x 3=90
Therefore the sum of the first two numbers= 92-90=2
Then the third number is= The sum of 5 numbers-(Therefore the sum of the first two numbers+Therefore the sum of the last two numbers)
=92-(2+56)=92-58=34