It is given in the question that the plane flies with 81 seats empty. The percentage of seats that are empty is 54%.It is required to find the total number of seats in the plane.
Let the number of seats in the plane = x
Then we can write the equation as
54x/100 = 81
54x = 100 * 81
x = 8100/54
= 150
So the plane has a total of 150 seats. I hope to have explained the method of solving the problem in details to you.