Let a = aircraft 1 seats
Let b = aircraft 2 seats
Let c = aircraft 3 seats
From the information given above, let's make basic equations.
We can begin to plug in values we know.
We now know that the second aircraft has 138 seats. Now we can plug in this value to find the value of the other seats. Let's start with the first aircraft.
We now know that the first aircraft has 189 seats. Let's now finally solve for the third aircraft.
Finally, we know that aircraft 3 has 84 seats. To check our work, let's make sure that each of these values add up to 411.
This is true, therefore the values are correct.
Aircraft 1: 189 seats
Aircraft 2: 138 seats
Aircraft 3: 84 seats