Answer:
Total number of tables of first type    = 23.
Total number of tables of second type = 7
Step-by-step explanation:
It is given that there are 30 tables in total and there are two types of tables.
Let's call the two seat tables, the first type as x and the second type as y.
∴                       x + y = 30             ......(1)
Also a total number of 81 people are seated. Therefore, 2x number of people would be seated on the the first type and 5y on the second type. Hence the equation becomes:
                      2x + 5y = 81             .....(2)
To solve (1) & (2) Multiply (1) by 2 and subtract, we get:
                           y = 7
Substituting y = 7 in (1), we get x = 23.
∴ The number of tables of first kind     = 23
 The number of tables of second kind  = 7
